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This is CS50

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cs50.ly/screen

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ide.cs50.io

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This is CS50

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#include <stdio.h>

int main(void)�{

printf("hello, world\n");

}

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01111111 01000101 01001100 01000110 00000010 00000001 00000001 00000000�00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000�00000010 00000000 00111110 00000000 00000001 00000000 00000000 00000000�10110000 00000101 01000000 00000000 00000000 00000000 00000000 00000000�01000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000�11010000 00010011 00000000 00000000 00000000 00000000 00000000 00000000�00000000 00000000 00000000 00000000 01000000 00000000 00111000 00000000�00001001 00000000 01000000 00000000 00100100 00000000 00100001 00000000�00000110 00000000 00000000 00000000 00000101 00000000 00000000 00000000�01000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000�01000000 00000000 01000000 00000000 00000000 00000000 00000000 00000000�01000000 00000000 01000000 00000000 00000000 00000000 00000000 00000000�11111000 00000001 00000000 00000000 00000000 00000000 00000000 00000000�11111000 00000001 00000000 00000000 00000000 00000000 00000000 00000000�00001000 00000000 00000000 00000000 00000000 00000000 00000000 00000000�00000011 00000000 00000000 00000000 00000100 00000000 00000000 00000000�00111000 00000010 00000000 00000000 00000000 00000000 00000000 00000000�...

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make hello

./hello

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clang hello.c

./a.out

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clang -o hello hello.c

./hello

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#include <stdio.h>

int main(void)

{

printf("hello, world\n");

}

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#include <cs50.h>

#include <stdio.h>

int main(void)

{

string name = get_string("What's your name? ");

printf("hello, %s\n", name);

}

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clang -o hello hello.c -lcs50

./hello

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make hello

./hello

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compiling

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preprocessing

compiling

...

string get_string(string prompt);

int printf(string format, ...);

...

int main(void)

{

string name = get_string("What's your name? ");

printf("hello, %s\n", name);

}

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preprocessing

compiling

assembling

linking

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...

string get_string(string prompt);

int printf(string format, ...);

...

int main(void)

{

string name = get_string("What's your name? ");

printf("hello, %s\n", name);

}

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...

main: # @main

.cfi_startproc

# BB#0:

pushq %rbp

.Ltmp0:

.cfi_def_cfa_offset 16

.Ltmp1:

.cfi_offset %rbp, -16

movq %rsp, %rbp

.Ltmp2:

.cfi_def_cfa_register %rbp

subq $16, %rsp

xorl %eax, %eax

movl %eax, %edi

movabsq $.L.str, %rsi

movb $0, %al

callq get_string

movabsq $.L.str.1, %rdi

movq %rax, -8(%rbp)

movq -8(%rbp), %rsi

movb $0, %al

callq printf

...

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...

main: # @main

.cfi_startproc

# BB#0:

pushq %rbp

.Ltmp0:

.cfi_def_cfa_offset 16

.Ltmp1:

.cfi_offset %rbp, -16

movq %rsp, %rbp

.Ltmp2:

.cfi_def_cfa_register %rbp

subq $16, %rsp

xorl %eax, %eax

movl %eax, %edi

movabsq $.L.str, %rsi

movb $0, %al

callq get_string

movabsq $.L.str.1, %rdi

movq %rax, -8(%rbp)

movq -8(%rbp), %rsi

movb $0, %al

callq printf

...

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...

main: # @main

.cfi_startproc

# BB#0:

pushq %rbp

.Ltmp0:

.cfi_def_cfa_offset 16

.Ltmp1:

.cfi_offset %rbp, -16

movq %rsp, %rbp

.Ltmp2:

.cfi_def_cfa_register %rbp

subq $16, %rsp

xorl %eax, %eax

movl %eax, %edi

movabsq $.L.str, %rsi

movb $0, %al

callq get_string

movabsq $.L.str.1, %rdi

movq %rax, -8(%rbp)

movq -8(%rbp), %rsi

movb $0, %al

callq printf

...

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preprocessing

compiling

assembling

linking

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...

main: # @main

.cfi_startproc

# BB#0:

pushq %rbp

.Ltmp0:

.cfi_def_cfa_offset 16

.Ltmp1:

.cfi_offset %rbp, -16

movq %rsp, %rbp

.Ltmp2:

.cfi_def_cfa_register %rbp

subq $16, %rsp

xorl %eax, %eax

movl %eax, %edi

movabsq $.L.str, %rsi

movb $0, %al

callq get_string

movabsq $.L.str.1, %rdi

movq %rax, -8(%rbp)

movq -8(%rbp), %rsi

movb $0, %al

callq printf

...

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01111111010001010100110001000110

00000010000000010000000100000000

00000000000000000000000000000000

00000001000000000011111000000000

00000001000000000000000000000000

00000000000000000000000000000000

10100000000000100000000000000000

00000000000000000000000000000000

01000000000000000000000000000000

00000000000000000100000000000000

00001010000000000000000100000000

01010101010010001000100111100101

01001000100000111110110000010000

00110001110000001000100111000111

01001000101111100000000000000000

00000000000000000000000000000000

00000000000000001011000000000000

11101000000000000000000000000000

00000000010010001011111100000000

00000000000000000000000000000000

hello.c

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hello.c

cs50.c

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hello.c

cs50.c

stdio.c

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01111111010001010100110001000110

00000010000000010000000100000000

00000000000000000000000000000000

00000001000000000011111000000000

00000001000000000000000000000000

00000000000000000000000000000000

10100000000000100000000000000000

00000000000000000000000000000000

01000000000000000000000000000000

00000000000000000100000000000000

00001010000000000000000100000000

01010101010010001000100111100101

01001000100000111110110000010000

00110001110000001000100111000111

01001000101111100000000000000000

00000000000000000000000000000000

00000000000000001011000000000000

11101000000000000000000000000000

00000000010010001011111100000000

00000000000000000000000000000000

00000000000000000000000001001000

...

cs50.c

stdio.c

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01111111010001010100110001000110

00000010000000010000000100000000

00000000000000000000000000000000

00000001000000000011111000000000

00000001000000000000000000000000

00000000000000000000000000000000

10100000000000100000000000000000

00000000000000000000000000000000

01000000000000000000000000000000

00000000000000000100000000000000

00001010000000000000000100000000

01010101010010001000100111100101

01001000100000111110110000010000

00110001110000001000100111000111

01001000101111100000000000000000

00000000000000000000000000000000

00000000000000001011000000000000

11101000000000000000000000000000

00000000010010001011111100000000

00000000000000000000000000000000

00000000000000000000000001001000

...

01111111010001010100110001000110

00000010000000010000000100000000

00000000000000000000000000000000

00000011000000000011111000000000

00000001000000000000000000000000

11000000000011110000000000000000

00000000000000000000000000000000

01000000000000000000000000000000

00000000000000000000000000000000

00101000001100100000000000000000

00000000000000000000000000000000

01000000000000000011100000000000

00000111000000000100000000000000

00011100000000000001100100000000

00000001000000000000000000000000

00000101000000000000000000000000

00000000000000000000000000000000

01011100001001010000000000000000

00000000000000000000000000000000

...

stdio.c

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01111111010001010100110001000110

00000010000000010000000100000000

00000000000000000000000000000000

00000001000000000011111000000000

00000001000000000000000000000000

00000000000000000000000000000000

10100000000000100000000000000000

00000000000000000000000000000000

01000000000000000000000000000000

00000000000000000100000000000000

00001010000000000000000100000000

01010101010010001000100111100101

01001000100000111110110000010000

00110001110000001000100111000111

01001000101111100000000000000000

00000000000000000000000000000000

00000000000000001011000000000000

11101000000000000000000000000000

00000000010010001011111100000000

00000000000000000000000000000000

00000000000000000000000001001000

...

01111111010001010100110001000110

00000010000000010000000100000000

00000000000000000000000000000000

00000011000000000011111000000000

00000001000000000000000000000000

11000000000011110000000000000000

00000000000000000000000000000000

01000000000000000000000000000000

00000000000000000000000000000000

00101000001100100000000000000000

00000000000000000000000000000000

01000000000000000011100000000000

00000111000000000100000000000000

00011100000000000001100100000000

00000001000000000000000000000000

00000101000000000000000000000000

00000000000000000000000000000000

01011100001001010000000000000000

00000000000000000000000000000000

...

00101111011011000110100101100010

01100011001011100111001101101111

00101110001101100010000000101111

01110101011100110111001000101111

01101100011010010110001000101111

01111000001110000011011001011111

00110110001101000010110101101100

01101001011011100111010101111000

00101101011001110110111001110101

00101111011011000110100101100010

01100011010111110110111001101111

01101110011100110110100001100001

01110010011001010110010000101110

01100001001000000010000001000001

01010011010111110100111001000101

01000101010001000100010101000100

00100000001010000010000000101111

01101100011010010110001000101111

01111000001110000011011001011111

00110110001101000010110101101100

01101001011011100111010101111000

00101101011001110110111001110101

00101111011011000110010000101101

01101100011010010110111001110101

01111000001011010111100000111000

00110110001011010011011000110100

...

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0111111101000101010011000100011000000010000000010000000100000000000000000000000000000000000000000000000000000000000000000000000000000001000000000011111000000000000000010000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000010100000000000100000000000000000000000000000000000000000000000000000000000000000000000000000000001000000000000000000000000000000000000000000000001000000000000000000101000000000000000010000000001010101010010001000100111100101010010001000001111101100000100000011000111000000100010011100011101001000101111100000000000000000000000000000000000000000000000000000000000000000101100000000000011101000000000000000000000000000000000000100100010111111000000000000000000000000000000000000000000000000000000000000000001001000...0111111101000101010011000100011000000010000000010000000100000000000000000000000000000000000000000000000000000000000000000000000000000011000000000011111000000000000000010000000000000000000000001100000000001111000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000000101000001100100000000000000000000000000000000000000000000000000000000000000000000000000000000001000000000000000011100000000000000001110000000001000000000000000001110000000000000110010000000000000001000000000000000000000000000001010000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000101110000100101000000000000000000000000000000000000000000000000...0010111101101100011010010110001001100011001011100111001101101111001011100011011000100000001011110111010101110011011100100010111101101100011010010110001000101111011110000011100000110110010111110011011000110100001011010110110001101001011011100111010101111000001011010110011101101110011101010010111101101100011010010110001001100011010111110110111001101111011011100111001101101000011000010111001001100101011001000010111001100001001000000010000001000001010100110101111101001110010001010100010101000100010001010100010000100000001010000010000000101111011011000110100101100010001011110111100000111000001101100101111100110110001101000010110101101100011010010110111001110101011110000010110101100111011011100111010100101111011011000110010000101101011011000110100101101110011101010111100000101101011110000011100000110110001011010011011000110100...

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preprocessing

compiling

assembling

linking

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compiling

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debugging

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help50

style50

check50

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help50

style50

check50

printf

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help50

style50

check50

printf

debug50

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help50

style50

check50

printf

debug50

ddb

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types

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bool

char

double

float

int

long

string

...

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bool 1 byte

char 1 byte

double 8 bytes

float 4 bytes

int 4 bytes

long 8 bytes

string ? bytes

...

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int score1 = 72;

int score2 = 73;

int score3 = 33;

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72 score1

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72 score1				73 score2

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72 score1				73 score2
33 score3

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00000000000000000000000001001000 score1				00000000000000000000000001001001 score2
00000000000000000000000000100001 score3

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int score1 = 72;

int score2 = 73;

int score3 = 33;

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arrays

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int scores[3];

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int scores[3];

scores[0] = 72;

scores[1] = 73;

scores[2] = 33;

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72 scores[0]				73 scores[1]
33 scores[2]

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constants

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char c = '#';

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# c

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35 c

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00100011 c

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char c1 = 'H';

char c2 = 'I';

char c3 = '!';

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H c1	I c2	! c3

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72 c1	73 c2	33 c3

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01001000 c1	01001001 c2	00100001 c3

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string s = "HI!";

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H	I s	!

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H s[0]	I s[1]	! s[2]

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H s[0]	I s[1]	! s[2]	\0 s[3]

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72 s[0]	73 s[1]	33 s[2]	0 s[3]

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H s	I	!	\0

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NUL

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string s = "HI!";

string t = "BYE!";

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H s	I	!	\0

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H s	I	!	\0	B t	Y	E	!
\0

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H s[0]	I s[1]	! s[2]	\0 s[3]	B t[0]	Y t[1]	E t[2]	! t[3]
\0 t[4]

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string words[2];

words[0] = "HI!";

words[1] = "BYE!";

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H words[0]	I	!	\0	B words[1]	Y	E	!
\0

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H words[0][0]	I words[0][1]	! words[0][2]	\0 words[0][3]	B words[1][0]	Y words[1][1]	E words[1][2]	! words[1][3]
\0 words[1][4]

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string

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manual pages

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command-line arguments

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#include <stdio.h>

int main(void)�{

...

}

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#include <stdio.h>

int main(void)�{

...

}

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#include <stdio.h>

int main(int argc, string argv[])�{

...

}

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exit status

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#include <stdio.h>

int main(int argc, string argv[])�{

...

}

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#include <stdio.h>

int main(int argc, string argv[])�{

...

}

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#include <stdio.h>

int main(void)�{

...

}

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readability

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"Mr. and Mrs. Dursley, of number four, Privet Drive, were proud to say that they were perfectly normal, thank you very much. They were the last people you'd expect to be involved in anything strange or mysterious, because they just didn't hold with such nonsense..."

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grade 7

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"In computational linguistics, authorship attribution is the task of predicting the author of a document of unknown authorship. This task is generally performed via the analysis of stylometric features — particular characteristics of an author’s writing that can be used to identify his or her works in contrast with the works of other authors…"

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grade 16

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cryptography

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input →

→ output

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plaintext →

→ ciphertext

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cipher

plaintext →

→ ciphertext

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cipher

plaintext →

→ ciphertext

key →

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I LOVE YOU →

→ ?

1 →

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I L O V E Y O U

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73 L O V E Y O U

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73 76 O V E Y O U

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73 76 79 V E Y O U

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73 76 79 86 E Y O U

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73 76 79 86 69 Y O U

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73 76 79 86 69 89 O U

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73 76 79 86 69 89 79 U

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73 76 79 86 69 89 79 85

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74 76 79 86 69 89 79 85

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74 77 79 86 69 89 79 85

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74 77 80 86 69 89 79 85

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74 77 80 87 69 89 79 85

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74 77 80 87 70 89 79 85

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74 77 80 87 70 90 79 85

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74 77 80 87 70 90 80 85

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74 77 80 87 70 90 80 86

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J 77 80 87 70 90 80 86

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J M 80 87 70 90 80 86

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J M P 87 70 90 80 86

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J M P W 70 90 80 86

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J M P W F 90 80 86

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J M P W F Z 80 86

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J M P W F Z P 86

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J M P W F Z P V

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I LOVE YOU →

→ J MPWF ZPV

1 →

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This is CS50