bash-pure, 75 bytes

Result

AC

Duration

842ms

Code [DL]

while read l;do
test ${l:1:1} = ${l:2:1}&&echo ${l:1:1}||echo ${l:4:1}
done

stdin

146 733
298 332
257 526
723 725
938 581
724 322
695 597
599 765
944 468
982 223
149 943
211 441
429 226
756 217
755 288
454 436
686 642
959 599
866 689
955 551
322 525
851 597
986 657
511 221
487 996
188 189
847 472
377 772
213 336
895 655
472 543
512 119

stdout

7
3
5
7
5
3
5
9
4
2
9
1
2
2
5
4
6
5
6
5
2
5
6
1
9
8
4
7
3
6
5
1

stderr

strace

14    execve("/bin/sh", ["/bin/sh", "/root/script", "/volume/CODE"], 0x7ffc05a25fa0 /* 9 vars */) = 0
15    execve("/usr/bin/realpath", ["realpath", "/volume/CODE"], 0x5650930c0d18 /* 9 vars */) = 0
15    +++ exited with 0 +++
14    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=15, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
16    execve("/bin/cp", ["cp", "-f", "/volume/CODE", "/opt/jails/bash-pure/code.bash"], 0x5650930c0d58 /* 9 vars */) = 0
16    +++ exited with 0 +++
14    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=16, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
17    execve("/bin/cat", ["cat", "-"], 0x5650941990d8 /* 9 vars */) = 0
18    execve("/usr/sbin/jk_chrootlaunch", ["jk_chrootlaunch", "-j", "/opt/jails/bash-pure", "-x", "/bin/bash", "/code.bash"], 0x5650941991c0 /* 9 vars */ <unfinished ...>
17    +++ exited with 0 +++
14    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=17, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
18    <... execve resumed>)             = 0
18    execve("/bin/bash", ["/bin/bash", "/code.bash"], 0x7ffece47da90 /* 9 vars */) = 0
18    +++ exited with 0 +++
14    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=18, si_uid=0, si_status=0, si_utime=0, si_stime=2} ---
19    execve("/bin/rm", ["rm", "/opt/jails/bash-pure/code.bash"], 0x5650930c0cb8 /* 9 vars */) = 0
19    +++ exited with 0 +++
14    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=19, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
14    +++ exited with 0 +++