lua, 81 bytes

Result

AC

Duration

894ms

Code [DL]

while 1 do a,b=io.read("*n","*n")c=a%10 io.write(c==a%100//10 and c or b//100)end

stdin

633 889
758 558
633 833
571 171
688 644
871 812
852 285
136 536
249 991
388 886
578 672
366 876
622 241
788 889
893 939
533 378
171 553
891 718
237 219
138 322
527 277
515 337
134 677
798 171
218 812
579 764
839 339
841 117
384 669
599 597
422 994
671 159

stdout

35318825986628935723236187316921

stderr

/usr/bin/lua5.3: /volume/CODE:1: attempt to perform arithmetic on a nil value (global 'a')
stack traceback:
	/volume/CODE:1: in main chunk
	[C]: in ?

strace

10    execve("/bin/sh", ["/bin/sh", "/root/script", "/volume/CODE"], 0x7ffec60f3670 /* 7 vars */) = 0
11    execve("/bin/cat", ["cat", "-"], 0x55a56339fd30 /* 7 vars */) = 0
12    execve("/usr/bin/lua5.3", ["/usr/bin/lua5.3", "/volume/CODE"], 0x55a56339fd40 /* 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 +++