golang, 97 bytes

Result

WA

Duration

1630ms

Code [DL]

package main
import."fmt"
func main(){for{a,b:=0,0;Scan(&a,&b);if b%110<9%a{a=b/10};Print(a%10)}}

stdin

532 326
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562 293
287 886
768 851
829 753
388 885
577 765
424 525
799 693
241 147
855 657
981 118
466 631
453 998
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919 918
811 119
926 343
413 119
344 134
411 994
689 275
882 365
347 775
592 629
253 531
916 762
712 199
522 772
355 139
671 882

stdout

29288987491516999163499272362758

stderr

panic: runtime error: integer divide by zero

goroutine 1 [running]:
main.main()
	/tmp/code.go:3 +0x1ec

strace

10    execve("/bin/sh", ["/bin/sh", "/root/script", "/volume/CODE"], 0x7ffe6c10b2b0 /* 7 vars */) = 0
11    execve("/usr/bin/realpath", ["realpath", "/volume/CODE"], 0x561fcb758d18 /* 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"], 0x561fcb758d38 /* 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"], 0x561fcc4b2028 /* 7 vars */) = 0
20    execve("/usr/lib/go/pkg/tool/linux_amd64/compile", ["/usr/lib/go/pkg/tool/linux_amd64"..., "-V=full"], 0xc0000efad0 /* 25 vars */) = 0
21    execve("/usr/lib/go/pkg/tool/linux_amd64/compile", ["/usr/lib/go/pkg/tool/linux_amd64"..., "-V=full"], 0xc00011d110 /* 25 vars */) = 0
24    +++ exited with 0 +++
25    +++ exited with 0 +++
26    +++ exited with 0 +++
23    +++ exited with 0 +++
20    +++ exited with 0 +++
22    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=20, si_uid=0, si_status=0, si_utime=0, si_stime=1} ---
27    execve("/usr/lib/go/pkg/tool/linux_amd64/asm", ["/usr/lib/go/pkg/tool/linux_amd64"..., "-V=full"], 0xc0000efe10 /* 25 vars */) = 0
31    +++ exited with 0 +++
28    +++ exited with 0 +++
29    +++ exited with 0 +++
30    +++ exited with 0 +++
21    +++ exited with 0 +++
15    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=21, si_uid=0, si_status=0, si_utime=0, si_stime=1} ---
32    execve("/usr/lib/go/pkg/tool/linux_amd64/asm", ["/usr/lib/go/pkg/tool/linux_amd64"..., "-V=full"], 0xc00011d2b0 /* 25 vars */) = 0
34    +++ exited with 0 +++
33    +++ exited with 0 +++
35    +++ exited with 0 +++
27    +++ exited with 0 +++
15    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=27, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
38    +++ exited with 0 +++
36    +++ exited with 0 +++
37    +++ exited with 0 +++
32    +++ exited with 0 +++
15    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=32, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
39    execve("/usr/lib/go/pkg/tool/linux_amd64/compile", ["/usr/lib/go/pkg/tool/linux_amd64"..., "-o", "/tmp/go-build227531576/b001/_pkg"..., "-trimpath", "/tmp/go-build227531576/b001=>", "-p", "main", "-complete", "-buildid", "FhQ0pp0HeGW79v-q_XqX/FhQ0pp0HeGW"..., "-goversion", "go1.13.10", "-D", "_/tmp", "-importcfg", "/tmp/go-build227531576/b001/impo"..., "-pack", "-c=2", "/tmp/code.go"], 0xc0004805b0 /* 25 vars */) = 0
42    +++ exited with 0 +++
41    +++ exited with 0 +++
40    +++ exited with 0 +++
39    +++ exited with 0 +++
15    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=39, si_uid=0, si_status=0, si_utime=1, si_stime=1} ---
43    execve("/usr/lib/go/pkg/tool/linux_amd64/link", ["/usr/lib/go/pkg/tool/linux_amd64"..., "-V=full"], 0xc0004808f0 /* 25 vars */) = 0
46    +++ exited with 0 +++
44    +++ exited with 0 +++
45    +++ exited with 0 +++
43    +++ exited with 0 +++
18    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=43, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
47    execve("/usr/lib/go/pkg/tool/linux_amd64/link", ["/usr/lib/go/pkg/tool/linux_amd64"..., "-o", "/tmp/go-build227531576/b001/exe/"..., "-importcfg", "/tmp/go-build227531576/b001/impo"..., "-buildmode=exe", "-buildid=cbtpbcnYB_niTzOq9LQW/Fh"..., "-extld=gcc", "/tmp/go-build227531576/b001/_pkg"...], 0xc000480dd0 /* 25 vars */) = 0
51    +++ exited with 0 +++
50    +++ exited with 0 +++
49    +++ exited with 0 +++
48    +++ exited with 0 +++
47    +++ exited with 0 +++
15    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=47, si_uid=0, si_status=0, si_utime=22, si_stime=5} ---
22    +++ 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=13} ---
52    execve("/bin/cat", ["cat", "-"], 0x561fcb758d08 /* 7 vars */) = 0
53    execve("/tmp/code", ["/tmp/code"], 0x561fcb758cf0 /* 7 vars */) = 0
52    +++ exited with 0 +++
10    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=52, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
54    +++ exited with 2 +++
57    +++ exited with 2 +++
56    +++ exited with 2 +++
55    +++ exited with 2 +++
53    +++ exited with 2 +++
10    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=53, si_uid=0, si_status=2, si_utime=0, si_stime=0} ---
58    execve("/bin/rm", ["rm", "/tmp/code.go", "/tmp/code"], 0x561fcb758cf0 /* 7 vars */) = 0
58    +++ exited with 0 +++
10    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=58, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
10    +++ exited with 0 +++