lua, 51 bytes

Result

WA

Duration

771ms

Code [DL]

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

stdin

369 886
549 425
554 115
482 282
672 727
618 183
944 441
768 441
788 883
244 115
466 993
638 832
783 428
367 741
594 442
799 151
223 339
746 725
238 231
911 619
175 775
399 513
155 565
633 322
785 364
118 112
857 596
518 855
957 358
828 783
955 756
462 822

stdout

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

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"], 0x7fffe772cce0 /* 7 vars */) = 0
11    execve("/bin/cat", ["cat", "-"], 0x55d479b8dd30 /* 7 vars */) = 0
12    execve("/usr/bin/lua5.3", ["/usr/bin/lua5.3", "/volume/CODE"], 0x55d479b8dd40 /* 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 +++