jq, 29 bytes

Result

AC

Duration

804ms

Code [DL]

scan("(.)\\1 | (.)")|join("")

stdin

712 335
569 663
811 122
498 982
228 889
276 517
811 117
899 399
711 266
373 386
633 436
383 812
273 373
422 415
843 632
711 448
215 451
881 864
133 369
433 735
283 885
541 346
941 142
731 164
148 481
185 785
877 221
464 779
738 889
744 446
143 863
741 315

stdout

3
6
1
9
8
5
1
9
1
3
3
8
3
2
6
1
4
8
3
3
8
3
1
1
4
7
7
7
8
4
8
3

stderr

strace

10    execve("/bin/sh", ["/bin/sh", "/root/script", "/volume/CODE"], 0x7fffebc76da0 /* 7 vars */) = 0
11    execve("/bin/cat", ["cat", "-"], 0x5575d5fbfcf8 /* 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} ---
13    execve("/usr/bin/jq", ["/usr/bin/jq", "-rR", "-f", "/volume/CODE"], 0x5575d7e82430 /* 7 vars */ <unfinished ...>
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 resumed>)             = 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=2, si_stime=0} ---
10    +++ exited with 0 +++