vim, 26 bytes

Result

WA

Duration

818ms

Code [DL]

:%s/\v.*(.)(\1| ).*/\1/
ZZ

Disassembly

:%s/\v.*(.)(\1| ).*/\1/<NL>ZZ

stdin

573 665
767 369
961 673
712 226
155 571
544 643
877 573
856 563
838 338
611 225
933 335
525 552
925 253
793 243
266 578
879 233
418 858
877 116
629 922
449 447
686 267
588 839
855 557
513 577
996 685
441 243
225 759
714 139
329 928
577 247
254 224
329 112

stdout

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

stderr

strace

12    execve("/bin/sh", ["/bin/sh", "/root/script", "/volume/CODE"], 0x7ffd88652af0 /* 9 vars */) = 0
13    execve("/bin/cat", ["cat", "-"], 0x56433fcded00 /* 9 vars */) = 0
13    +++ exited with 0 +++
12    --- 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/vim", ["/usr/bin/vim", "-N", "-u", "NONE", "-i", "NONE", "-s", "/volume/CODE", "/tmp/out"], 0x5643400cb288 /* 10 vars */) = 0
14    +++ exited with 0 +++
12    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=14, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
15    execve("/bin/cat", ["cat", "/tmp/out"], 0x56433fcdec98 /* 9 vars */) = 0
15    +++ exited with 0 +++
12    --- 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/rm", ["rm", "/tmp/out"], 0x56433fcdec98 /* 9 vars */) = 0
16    +++ exited with 0 +++
12    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=16, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
12    +++ exited with 0 +++