golang, 101 bytes

Result

AC

Duration

2235ms

Code [DL]

package main;import."fmt";func main(){for{s,t:="","";Scan(&s,&t);Print((s+t)[3-1/(s[1]^s[2]+1)]&15)}}

stdin

856 652
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811 669
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277 775
518 864
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271 177
328 551
257 372
966 668
942 443
946 332
877 972
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186 881
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284 239
588 817
799 775
497 385
751 513
155 589
344 947
779 938
762 223
428 727
587 988
169 628
744 388
277 142

stdout

62127892153643728928935549279647

stderr

panic: runtime error: index out of range [1] with length 0

goroutine 1 [running]:
main.main()
	/tmp/code.go:1 +0x266

strace

10    execve("/bin/sh", ["/bin/sh", "/root/script", "/volume/CODE"], 0x7ffd962d7120 /* 7 vars */) = 0
11    execve("/usr/bin/realpath", ["realpath", "/volume/CODE"], 0x55af0059bd18 /* 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    execve("/bin/ln", ["ln", "-sf", "/volume/CODE", "/tmp/code.go"], 0x55af0059bd38 /* 7 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("/usr/bin/go", ["/usr/bin/go", "build", "-o", "/tmp/code", "/tmp/code.go"], 0x55af018ee028 /* 7 vars */) = 0
20    execve("/usr/lib/go/pkg/tool/linux_amd64/compile", ["/usr/lib/go/pkg/tool/linux_amd64"..., "-V=full"], 0xc000414270 /* 25 vars */) = 0
21    execve("/usr/lib/go/pkg/tool/linux_amd64/compile", ["/usr/lib/go/pkg/tool/linux_amd64"..., "-V=full"], 0xc0003fef70 /* 25 vars */) = 0
24    +++ exited with 0 +++
26    +++ exited with 0 +++
23    +++ exited with 0 +++
22    +++ exited with 0 +++
20    +++ exited with 0 +++
18    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=20, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
29    +++ exited with 0 +++
27    +++ exited with 0 +++
28    +++ exited with 0 +++
30    +++ exited with 0 +++
21    +++ exited with 0 +++
18    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=21, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
31    execve("/usr/lib/go/pkg/tool/linux_amd64/asm", ["/usr/lib/go/pkg/tool/linux_amd64"..., "-V=full"], 0xc000414410 /* 25 vars */) = 0
32    execve("/usr/lib/go/pkg/tool/linux_amd64/asm", ["/usr/lib/go/pkg/tool/linux_amd64"..., "-V=full"], 0xc0003ff1e0 /* 25 vars */) = 0
35    +++ exited with 0 +++
34    +++ exited with 0 +++
33    +++ exited with 0 +++
36    +++ exited with 0 +++
31    +++ exited with 0 +++
13    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=31, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
39    +++ exited with 0 +++
38    +++ exited with 0 +++
37    +++ exited with 0 +++
40    +++ exited with 0 +++
32    +++ exited with 0 +++
18    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=32, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
42    execve("/usr/lib/go/pkg/tool/linux_amd64/compile", ["/usr/lib/go/pkg/tool/linux_amd64"..., "-o", "/tmp/go-build322448434/b001/_pkg"..., "-trimpath", "/tmp/go-build322448434/b001=>", "-p", "main", "-complete", "-buildid", "Lxwq5-6LpwMaZMxU44WE/Lxwq5-6LpwM"..., "-goversion", "go1.13.10", "-D", "_/tmp", "-importcfg", "/tmp/go-build322448434/b001/impo"..., "-pack", "-c=2", "/tmp/code.go"], 0xc0001305b0 /* 25 vars */) = 0
44    +++ exited with 0 +++
43    +++ exited with 0 +++
45    +++ exited with 0 +++
46    +++ exited with 0 +++
42    +++ exited with 0 +++
15    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=42, si_uid=0, si_status=0, si_utime=0, si_stime=1} ---
47    execve("/usr/lib/go/pkg/tool/linux_amd64/link", ["/usr/lib/go/pkg/tool/linux_amd64"..., "-V=full"], 0xc000130a90 /* 25 vars */) = 0
50    +++ exited with 0 +++
49    +++ exited with 0 +++
48    +++ exited with 0 +++
51    +++ exited with 0 +++
47    +++ exited with 0 +++
19    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=47, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
52    execve("/usr/lib/go/pkg/tool/linux_amd64/link", ["/usr/lib/go/pkg/tool/linux_amd64"..., "-o", "/tmp/go-build322448434/b001/exe/"..., "-importcfg", "/tmp/go-build322448434/b001/impo"..., "-buildmode=exe", "-buildid=ffjRVVu65XROGfDaCWbI/Lx"..., "-extld=gcc", "/tmp/go-build322448434/b001/_pkg"...], 0xc000130f70 /* 25 vars */) = 0
55    +++ exited with 0 +++
54    +++ exited with 0 +++
53    +++ exited with 0 +++
56    +++ exited with 0 +++
52    +++ exited with 0 +++
19    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=52, si_uid=0, si_status=0, si_utime=21, si_stime=5} ---
41    +++ exited with 0 +++
25    +++ exited with 0 +++
19    +++ exited with 0 +++
18    +++ exited with 0 +++
17    +++ exited with 0 +++
16    +++ exited with 0 +++
15    +++ exited with 0 +++
14    +++ exited with 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=6, si_stime=9} ---
57    execve("/bin/cat", ["cat", "-"], 0x55af0059bd08 /* 7 vars */ <unfinished ...>
58    execve("/tmp/code", ["/tmp/code"], 0x55af0059bcf0 /* 7 vars */) = 0
57    <... execve resumed>)             = 0
57    +++ exited with 0 +++
10    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=57, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
59    +++ exited with 2 +++
62    +++ exited with 2 +++
61    +++ exited with 2 +++
60    +++ exited with 2 +++
58    +++ exited with 2 +++
10    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=58, si_uid=0, si_status=2, si_utime=0, si_stime=0} ---
63    execve("/bin/rm", ["rm", "/tmp/code.go", "/tmp/code"], 0x55af0059bcf0 /* 7 vars */) = 0
63    +++ exited with 0 +++
10    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=63, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
10    +++ exited with 0 +++