vim, 25 bytes

Result

WA

Duration

980ms

Code [DL]

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

Disassembly

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

stdin

115 119
633 177
946 376
355 355
577 754
348 897
766 765
466 681
693 361
593 395
658 351
593 182
345 957
134 394
594 341
759 556
367 524
411 664
886 224
688 886
187 785
828 889
973 733
274 663
911 446
119 994
566 661
817 629
288 947
371 678
721 215
739 311

stdout

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

stderr

strace

10    execve("/bin/sh", ["/bin/sh", "/root/script", "/volume/CODE"], 0x7ffdb2195380 /* 9 vars */) = 0
11    execve("/bin/cat", ["cat", "-"], 0x5568088bdd00 /* 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"], 0x556808b71288 /* 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=1} ---
13    execve("/bin/cat", ["cat", "/tmp/out"], 0x5568088bdc98 /* 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"], 0x5568088bdc98 /* 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 +++