reasonml, 183 bytes

Result

WA

Duration

1200ms

Code [DL]

for (i in 0 to 31) {
  let a = Node.Fs.readFileSync("/dev/stdin", `utf8);
  if (a.[1] == a.[2]) {
    Js.log(String.sub(a, 2, 2));
  } else {
    Js.log(String.sub(a, 4, 4));
  };
};

stdin

678 116
157 672
851 586
524 983
887 338
833 553
256 748
787 889
334 441
455 556
877 472
986 784
523 932
472 724
318 161
614 419
942 187
244 415
931 552
867 781
244 758
155 365
769 695
587 772
761 665
195 546
143 342
133 341
744 645
858 655
699 771
988 889

stdout

stderr

  Warning number 35
  /tmp/code.re 1:1-8:1
  
  1 │ for (i in 0 to 31) {
  2 │   let a = Node.Fs.readFileSync("/dev/stdin", `utf8);
  . │ ...
  7 │   };
  8 │ };
  
  unused for-loop index i.
  internal/modules/cjs/loader.js:983
  throw err;
  ^

Error: Cannot find module 'bs-platform/lib/js/string.js'
Require stack:
- /tmp/code.js
    at Function.Module._resolveFilename (internal/modules/cjs/loader.js:980:15)
    at Function.Module._load (internal/modules/cjs/loader.js:862:27)
    at Module.require (internal/modules/cjs/loader.js:1042:19)
    at require (internal/modules/cjs/helpers.js:77:18)
    at Object.<anonymous> (/tmp/code.js:5:16)
    at Module._compile (internal/modules/cjs/loader.js:1156:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1176:10)
    at Module.load (internal/modules/cjs/loader.js:1000:32)
    at Function.Module._load (internal/modules/cjs/loader.js:899:14)
    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:74:12) {
  code: 'MODULE_NOT_FOUND',
  requireStack: [ '/tmp/code.js' ]
}

strace

11    execve("/bin/sh", ["/bin/sh", "/root/script", "/volume/CODE"], 0x7fff4dc50570 /* 9 vars */) = 0
12    execve("/usr/bin/realpath", ["realpath", "/volume/CODE"], 0x55aba4139d18 /* 9 vars */) = 0
12    +++ exited with 0 +++
11    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=12, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
13    execve("/bin/ln", ["ln", "-sf", "/volume/CODE", "/tmp/code.re"], 0x55aba4139d38 /* 9 vars */) = 0
13    +++ exited with 0 +++
11    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=13, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
14    execve("/usr/bin/bsc", ["/usr/bin/bsc", "/tmp/code.re"], 0x55aba4139d20 /* 9 vars */) = 0
14    execve("/bin/node", ["node", "/usr/bin/bsc", "/tmp/code.re"], 0x7fffb57d3d90 /* 9 vars */) = -1 ENOENT (No such file or directory)
14    execve("/usr/local/sbin/node", ["node", "/usr/bin/bsc", "/tmp/code.re"], 0x7fffb57d3d90 /* 9 vars */) = -1 ENOENT (No such file or directory)
14    execve("/usr/local/bin/node", ["node", "/usr/bin/bsc", "/tmp/code.re"], 0x7fffb57d3d90 /* 9 vars */) = -1 ENOENT (No such file or directory)
14    execve("/usr/sbin/node", ["node", "/usr/bin/bsc", "/tmp/code.re"], 0x7fffb57d3d90 /* 9 vars */) = -1 ENOENT (No such file or directory)
14    execve("/usr/bin/node", ["node", "/usr/bin/bsc", "/tmp/code.re"], 0x7fffb57d3d90 /* 9 vars */) = 0
21    execve("/usr/lib/node_modules/bs-platform/linux/bsc.exe", ["/usr/lib/node_modules/bs-platfor"..., "/tmp/code.re"], 0x55c4555cbf60 /* 9 vars */) = 0
22    execve("/bin/sh", ["sh", "-c", "/usr/lib/node_modules/bs-platfor"...], 0x7ffffcbfd090 /* 9 vars */) = 0
22    execve("/usr/lib/node_modules/bs-platform/linux/refmt.exe", ["/usr/lib/node_modules/bs-platfor"..., "--print=binary", "/tmp/code.re"], 0x564a40fb6090 /* 9 vars */) = 0
22    +++ exited with 0 +++
21    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=22, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
21    +++ exited with 0 +++
14    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=21, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
17    +++ exited with 0 +++
16    +++ exited with 0 +++
18    +++ exited with 0 +++
19    +++ exited with 0 +++
15    +++ exited with 0 +++
20    +++ exited with 0 +++
14    +++ exited with 0 +++
11    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=14, si_uid=0, si_status=0, si_utime=3, si_stime=1} ---
23    execve("/bin/cat", ["cat", "-"], 0x55aba4139d38 /* 9 vars */ <unfinished ...>
24    execve("/usr/bin/node", ["/usr/bin/node", "/tmp/code.js"], 0x55aba4139d48 /* 9 vars */) = 0
23    <... execve resumed>)             = 0
23    +++ exited with 0 +++
11    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=23, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
27    +++ exited with 0 +++
26    +++ exited with 0 +++
28    +++ exited with 0 +++
29    +++ exited with 0 +++
25    +++ exited with 0 +++
30    +++ exited with 1 +++
24    +++ exited with 1 +++
11    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=24, si_uid=0, si_status=1, si_utime=3, si_stime=2} ---
31    execve("/bin/rm", ["rm", "/tmp/code.js", "/tmp/code.re"], 0x55aba4139cf0 /* 9 vars */) = 0
31    +++ exited with 0 +++
11    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=31, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
11    +++ exited with 0 +++