lua, 96 bytes

Result

AC

Duration

940ms

Code [DL]

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

stdin

937 338
569 962
611 188
299 224
194 428
833 637
355 553
857 771
748 683
422 642
677 224
932 382
161 747
694 746
182 225
582 286
815 942
735 736
669 929
351 887
981 368
411 176
856 535
433 331
915 155
688 266
799 795
382 547
795 995
869 691
593 795
519 779

stdout

39194357627377229798315318959677

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"], 0x7ffd5a69d9c0 /* 7 vars */) = 0
11    execve("/bin/cat", ["cat", "-"], 0x5583d91e4d30 /* 7 vars */) = 0
12    execve("/usr/bin/lua5.3", ["/usr/bin/lua5.3", "/volume/CODE"], 0x5583d91e4d40 /* 7 vars */ <unfinished ...>
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 resumed>)             = 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 +++