lua, 51 bytes

Result

AC

Duration

791ms

Code [DL]

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

stdin

544 441
748 842
233 346
233 976
945 278
987 876
554 976
998 991
181 535
311 516
141 221
946 348
891 987
455 665
787 717
652 225
472 573
812 927
266 668
367 664
629 994
515 514
935 359
492 762
522 771
724 212
866 691
411 721
922 929
292 629
767 991
126 653

stdout

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

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

11    execve("/bin/sh", ["/bin/sh", "/root/script", "/volume/CODE"], 0x7ffe836c8a70 /* 7 vars */) = 0
12    execve("/bin/cat", ["cat", "-"], 0x56441affed30 /* 7 vars */ <unfinished ...>
13    execve("/usr/bin/lua5.3", ["/usr/bin/lua5.3", "/volume/CODE"], 0x56441affed40 /* 7 vars */ <unfinished ...>
12    <... execve resumed>)             = 0
13    <... execve resumed>)             = 0
12    +++ exited with 0 +++
11    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=12, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
13    +++ exited with 1 +++
11    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=13, si_uid=0, si_status=1, si_utime=0, si_stime=0} ---
11    +++ exited with 1 +++