reasonml, 187 bytes

Result

WA

Duration

962ms

Code [DL]

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

stdin

488 859
488 911
869 997
183 551
748 446
428 384
766 369
191 533
398 896
144 417
434 332
176 679
824 498
725 727
315 834
588 887
344 226
199 795
146 862
915 161
948 219
182 811
572 285
749 492
388 728
718 916
568 883
588 886
841 669
488 993
514 143
314 883

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

10    execve("/bin/sh", ["/bin/sh", "/root/script", "/volume/CODE"], 0x7ffcb52f60b0 /* 9 vars */) = 0
11    execve("/usr/bin/realpath", ["realpath", "/volume/CODE"], 0x56215a7ccd18 /* 9 vars */) = 0
11    +++ exited with 0 +++
10    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=11, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
12    execve("/bin/ln", ["ln", "-sf", "/volume/CODE", "/tmp/code.re"], 0x56215a7ccd38 /* 9 vars */) = 0
12    +++ exited with 0 +++
10    --- 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("/usr/bin/bsc", ["/usr/bin/bsc", "/tmp/code.re"], 0x56215a7ccd20 /* 9 vars */) = 0
13    execve("/bin/node", ["node", "/usr/bin/bsc", "/tmp/code.re"], 0x7ffe0ff37860 /* 9 vars */) = -1 ENOENT (No such file or directory)
13    execve("/usr/local/sbin/node", ["node", "/usr/bin/bsc", "/tmp/code.re"], 0x7ffe0ff37860 /* 9 vars */) = -1 ENOENT (No such file or directory)
13    execve("/usr/local/bin/node", ["node", "/usr/bin/bsc", "/tmp/code.re"], 0x7ffe0ff37860 /* 9 vars */) = -1 ENOENT (No such file or directory)
13    execve("/usr/sbin/node", ["node", "/usr/bin/bsc", "/tmp/code.re"], 0x7ffe0ff37860 /* 9 vars */) = -1 ENOENT (No such file or directory)
13    execve("/usr/bin/node", ["node", "/usr/bin/bsc", "/tmp/code.re"], 0x7ffe0ff37860 /* 9 vars */) = 0
20    execve("/usr/lib/node_modules/bs-platform/linux/bsc.exe", ["/usr/lib/node_modules/bs-platfor"..., "/tmp/code.re"], 0x55ceb9737f60 /* 9 vars */) = 0
21    execve("/bin/sh", ["sh", "-c", "/usr/lib/node_modules/bs-platfor"...], 0x7ffe6dbd71f0 /* 9 vars */) = 0
21    execve("/usr/lib/node_modules/bs-platform/linux/refmt.exe", ["/usr/lib/node_modules/bs-platfor"..., "--print=binary", "/tmp/code.re"], 0x5594c3f7a090 /* 9 vars */) = 0
21    +++ exited with 0 +++
20    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=21, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
20    +++ exited with 0 +++
13    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=20, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
15    +++ exited with 0 +++
16    +++ exited with 0 +++
14    +++ exited with 0 +++
17    +++ exited with 0 +++
18    +++ exited with 0 +++
19    +++ exited with 0 +++
13    +++ exited with 0 +++
10    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=13, si_uid=0, si_status=0, si_utime=4, si_stime=0} ---
22    execve("/bin/cat", ["cat", "-"], 0x56215a7ccd38 /* 9 vars */ <unfinished ...>
23    execve("/usr/bin/node", ["/usr/bin/node", "/tmp/code.js"], 0x56215a7ccd48 /* 9 vars */ <unfinished ...>
22    <... execve resumed>)             = 0
23    <... execve resumed>)             = 0
22    +++ exited with 0 +++
10    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=22, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
27    +++ exited with 0 +++
28    +++ exited with 0 +++
26    +++ exited with 0 +++
25    +++ exited with 0 +++
24    +++ exited with 0 +++
29    +++ exited with 1 +++
23    +++ exited with 1 +++
10    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=23, si_uid=0, si_status=1, si_utime=4, si_stime=2} ---
30    execve("/bin/rm", ["rm", "/tmp/code.js", "/tmp/code.re"], 0x56215a7cccf0 /* 9 vars */) = 0
30    +++ exited with 0 +++
10    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=30, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
10    +++ exited with 0 +++