vim, 25 bytes

Result

WA

Duration

775ms

Code [DL]

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

Disassembly

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

stdin

171 715
947 743
678 733
833 352
147 649
135 442
455 683
133 234
672 778
699 915
787 727
311 339
584 886
515 553
544 112
341 345
899 991
257 471
458 911
283 815
766 662
677 475
939 936
989 972
939 662
853 638
439 369
345 558
537 375
322 755
948 697
732 698

stdout

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

stderr

strace

10    execve("/bin/sh", ["/bin/sh", "/root/script", "/volume/CODE"], 0x7ffe4dbc07a0 /* 9 vars */) = 0
11    execve("/bin/cat", ["cat", "-"], 0x55fad99d9d00 /* 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("/usr/bin/vim", ["/usr/bin/vim", "-N", "-u", "NONE", "-i", "NONE", "-s", "/volume/CODE", "/tmp/out"], 0x55fada5cc288 /* 10 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("/bin/cat", ["cat", "/tmp/out"], 0x55fad99d9c98 /* 9 vars */) = 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=0, si_stime=0} ---
14    execve("/bin/rm", ["rm", "/tmp/out"], 0x55fad99d9c98 /* 9 vars */) = 0
14    +++ exited with 0 +++
10    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=14, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
10    +++ exited with 0 +++