golang, 117 bytes

Result

AC

Duration

1538ms

Code [DL]

package main
import."fmt"
func main(){s,t,i:="","",0;for i<32{Scan(&s, &t);if s[1]==s[2]{t=s[1:]};Print(t[0:1]);i++}}

stdin

788 774
254 152
728 281
866 167
415 213
854 542
348 892
157 757
655 522
568 422
896 145
299 936
659 581
288 248
711 113
982 361
379 946
463 234
136 469
239 992
675 667
489 884
944 773
845 552
452 553
396 971
663 361
151 375
833 336
877 572
195 887
944 181

stdout

81262587541958139249684559333784

stderr

strace

10    execve("/bin/sh", ["/bin/sh", "/root/script", "/volume/CODE"], 0x7ffd8cedda40 /* 7 vars */) = 0
11    execve("/usr/bin/realpath", ["realpath", "/volume/CODE"], 0x55f40bfaed18 /* 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"], 0x55f40bfaed38 /* 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"], 0x55f40dd0e028 /* 7 vars */) = 0
20    execve("/usr/lib/go/pkg/tool/linux_amd64/compile", ["/usr/lib/go/pkg/tool/linux_amd64"..., "-V=full"], 0xc00049e5b0 /* 25 vars */) = 0
21    execve("/usr/lib/go/pkg/tool/linux_amd64/compile", ["/usr/lib/go/pkg/tool/linux_amd64"..., "-V=full"], 0xc0001188f0 /* 25 vars */) = 0
22    ????( <unfinished ...>
23    +++ exited with 0 +++
22    +++ exited with 0 +++
24    +++ exited with 0 +++
20    +++ exited with 0 +++
15    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=20, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
25    execve("/usr/lib/go/pkg/tool/linux_amd64/asm", ["/usr/lib/go/pkg/tool/linux_amd64"..., "-V=full"], 0xc00049e820 /* 25 vars */) = 0
27    +++ exited with 0 +++
28    +++ exited with 0 +++
26    +++ exited with 0 +++
21    +++ exited with 0 +++
19    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=21, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
30    execve("/usr/lib/go/pkg/tool/linux_amd64/asm", ["/usr/lib/go/pkg/tool/linux_amd64"..., "-V=full"], 0xc000118b60 /* 25 vars */) = 0
33    +++ exited with 0 +++
34    +++ exited with 0 +++
35    +++ exited with 0 +++
32    +++ exited with 0 +++
25    +++ exited with 0 +++
31    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=25, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
37    +++ exited with 0 +++
36    +++ exited with 0 +++
38    +++ exited with 0 +++
30    +++ exited with 0 +++
31    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=30, 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-build850536005/b001/_pkg"..., "-trimpath", "/tmp/go-build850536005/b001=>", "-p", "main", "-complete", "-buildid", "K9WDVKIeNtL0SH8kUk1M/K9WDVKIeNtL"..., "-goversion", "go1.13.10", "-D", "_/tmp", "-importcfg", "/tmp/go-build850536005/b001/impo"..., "-pack", "-c=2", "/tmp/code.go"], 0xc000444410 /* 25 vars */) = 0
43    +++ exited with 0 +++
41    +++ exited with 0 +++
42    +++ exited with 0 +++
40    +++ exited with 0 +++
39    +++ exited with 0 +++
29    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=39, si_uid=0, si_status=0, si_utime=1, si_stime=1} ---
44    execve("/usr/lib/go/pkg/tool/linux_amd64/link", ["/usr/lib/go/pkg/tool/linux_amd64"..., "-V=full"], 0xc00035c270 /* 25 vars */) = 0
46    +++ exited with 0 +++
48    +++ exited with 0 +++
47    +++ exited with 0 +++
45    +++ exited with 0 +++
44    +++ exited with 0 +++
13    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=44, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
49    execve("/usr/lib/go/pkg/tool/linux_amd64/link", ["/usr/lib/go/pkg/tool/linux_amd64"..., "-o", "/tmp/go-build850536005/b001/exe/"..., "-importcfg", "/tmp/go-build850536005/b001/impo"..., "-buildmode=exe", "-buildid=_AwDx3BAFuN7-MBJXSWV/K9"..., "-extld=gcc", "/tmp/go-build850536005/b001/_pkg"...], 0xc00035c750 /* 25 vars */) = 0
52    +++ exited with 0 +++
51    +++ exited with 0 +++
50    +++ exited with 0 +++
49    +++ exited with 0 +++
13    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=49, si_uid=0, si_status=0, si_utime=20, si_stime=4} ---
31    +++ exited with 0 +++
29    +++ 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=5, si_stime=12} ---
53    execve("/bin/cat", ["cat", "-"], 0x55f40bfaed08 /* 7 vars */ <unfinished ...>
54    execve("/tmp/code", ["/tmp/code"], 0x55f40bfaecf0 /* 7 vars */ <unfinished ...>
53    <... execve resumed>)             = 0
54    <... execve resumed>)             = 0
53    +++ exited with 0 +++
10    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=53, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
57    +++ exited with 0 +++
56    +++ exited with 0 +++
55    +++ exited with 0 +++
54    +++ exited with 0 +++
10    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=54, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
58    execve("/bin/rm", ["rm", "/tmp/code.go", "/tmp/code"], 0x55f40bfaecf0 /* 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 +++