lua, 50 bytes

Result

AC

Duration

791ms

Code [DL]

repeat until print(io.read():match("(.) ?%1")or 1)

stdin

638 883
241 844
942 448
398 723
955 455
819 314
762 516
812 212
439 451
626 665
456 542
299 339
768 821
253 433
155 554
353 989
389 887
341 477
614 419
726 448
299 954
838 856
267 884
511 283
677 297
922 229
287 277
811 774
788 817
711 813
263 638
493 933

stdout

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

stderr

/usr/bin/lua5.3: /volume/CODE:1: attempt to index a nil value
stack traceback:
	/volume/CODE:1: in main chunk
	[C]: in ?

strace

10    execve("/bin/sh", ["/bin/sh", "/root/script", "/volume/CODE"], 0x7ffdd2f490f0 /* 7 vars */) = 0
12    execve("/usr/bin/lua5.3", ["/usr/bin/lua5.3", "/volume/CODE"], 0x5621856ead40 /* 7 vars */) = 0
11    execve("/bin/cat", ["cat", "-"], 0x5621856ead30 /* 7 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    +++ exited with 1 +++
10    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=12, si_uid=0, si_status=1, si_utime=0, si_stime=0} ---
10    +++ exited with 1 +++