ruby, 28 bytes

Result

AC

Duration

915ms

Code [DL]

loop{$><<gets[/(.)\1 /?2:4]}

stdin

674 743
637 352
598 399
933 355
846 441
575 554
593 447
353 558
289 441
275 652
622 524
655 578
223 934
297 795
699 553
354 639
526 663
526 396
512 818
655 946
622 932
634 289
622 221
282 114
966 862
522 113
826 626
144 442
367 729
425 587
912 148
662 629

stdout

73334545462597966385222162647516

stderr

/volume/CODE:1: warning: regex literal in condition
/volume/CODE:1:in `block in <main>': undefined method `[]' for nil:NilClass (NoMethodError)
	from /volume/CODE:1:in `loop'
	from /volume/CODE:1:in `<main>'

strace

10    execve("/bin/sh", ["/bin/sh", "/root/script", "/volume/CODE"], 0x7fff4dfdec90 /* 9 vars */) = 0
11    execve("/bin/cat", ["cat", "-"], 0x555f6ab7ed40 /* 9 vars */) = 0
12    execve("/usr/local/ruby-2.7.1/bin/ruby", ["/usr/local/ruby-2.7.1/bin/ruby", "/volume/CODE"], 0x555f6ab7ed60 /* 9 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=5, si_stime=3} ---
10    +++ exited with 1 +++