c-gcc, 128 bytes

Result

AC

Code [DL]

int i,a,b;main(){for(;a<50;a++){for(b=i=0;b<8;b++){i+=getchar()&1;i*=2;}getchar();i/=2;for(b=0;i>0;)i-=b++;putchar(i<0?48:49);}}

stdin

01111000
10111101
01010101
10000101
00001010
11100111
10011001
01101001
10011010
00011101
11000101
01011011
11011000
11100111
11101101
01001111
01000010
01100001
01110000
11000111
01001000
11010010
11111100
10101011
01001110
00100100
00100101
00110111
00000110
00110001
10111110
00101010
10001000
10000011
00101101
10010010
11011011
11111101
00000001
00001111
00000110
11100011
10111011
00010101
00000011
11000010
01000111
00011100
00000000
00101011

stdout

10001111000101001000010111011010101001111001100110

stderr

/tmp/code.c:1:11: warning: return type defaults to ‘int’ [-Wimplicit-int]
 int i,a,b;main(){for(;a<50;a++){for(b=i=0;b<8;b++){i+=getchar()&1;i*=2;}getchar();i/=2;for(b=0;i>0;)i-=b++;putchar(i<0?48:49);}}
           ^
/tmp/code.c: In function ‘main’:
/tmp/code.c:1:55: warning: implicit declaration of function ‘getchar’ [-Wimplicit-function-declaration]
 int i,a,b;main(){for(;a<50;a++){for(b=i=0;b<8;b++){i+=getchar()&1;i*=2;}getchar();i/=2;for(b=0;i>0;)i-=b++;putchar(i<0?48:49);}}
                                                       ^
/tmp/code.c:1:108: warning: implicit declaration of function ‘putchar’ [-Wimplicit-function-declaration]
 int i,a,b;main(){for(;a<50;a++){for(b=i=0;b<8;b++){i+=getchar()&1;i*=2;}getchar();i/=2;for(b=0;i>0;)i-=b++;putchar(i<0?48:49);}}
                                                                                                            ^

strace