oh, 95 bytes

Result

AC

Duration

997ms

Code [DL]

define a:""::split:readline
echo:if(eq($a::get 1):$a::get 2)($a::get 1)else:$a::get 4
source $0

stdin

889 998
571 998
466 118
762 669
712 315
969 962
966 233
544 328
266 996
522 928
766 445
136 632
183 858
633 336
933 733
534 193
788 837
818 845
228 624
155 547
691 998
322 226
179 746
975 754
779 792
692 219
865 355
695 244
647 279
348 221
775 317
365 552

stdout

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

stderr

boot.oh: 360: error/runtime: argument 1 (of 1) is invalid

strace

10    execve("/bin/sh", ["/bin/sh", "/root/script", "/volume/CODE"], 0x7ffdd7224df0 /* 7 vars */) = 0
11    execve("/bin/cat", ["cat", "-"], 0x5649012ae048 /* 7 vars */ <unfinished ...>
13    execve("/usr/bin/go", ["/usr/bin/go", "env", "GOPATH"], 0x5649012ae078 /* 7 vars */) = 0
11    <... execve resumed>)             = 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} ---
16    +++ exited with 0 +++
17    +++ exited with 0 +++
15    +++ exited with 0 +++
14    +++ exited with 0 +++
13    +++ exited with 0 +++
12    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=13, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
12    execve("/root/go/bin/oh", ["/root/go/bin/oh", "/volume/CODE"], 0x5649012ae068 /* 7 vars */) = 0
23    +++ exited with 0 +++
21    +++ exited with 0 +++
19    +++ exited with 0 +++
18    +++ exited with 0 +++
20    +++ exited with 0 +++
22    +++ exited with 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=3, si_stime=9} ---
10    +++ exited with 0 +++