vim, 25 bytes

Result

WA

Duration

871ms

Code [DL]

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

Disassembly

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

stdin

193 977
393 932
931 973
665 479
241 113
948 448
594 498
546 613
522 112
753 331
179 817
793 998
637 443
755 554
944 914
885 453
137 236
272 677
223 138
199 195
991 914
655 599
311 186
238 839
833 483
852 784
584 872
388 288
528 874
988 996
499 991
126 773

stdout

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

stderr

strace

10    execve("/bin/sh", ["/bin/sh", "/root/script", "/volume/CODE"], 0x7ffc389cbdf0 /* 9 vars */) = 0
11    execve("/bin/cat", ["cat", "-"], 0x563f96ceed00 /* 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"], 0x563f981bd288 /* 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"], 0x563f96ceec98 /* 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"], 0x563f96ceec98 /* 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 +++