vim, 190 bytes

Result

WA

Code [DL]

gg
dd
10p
gg
dd
:1,2s/[^0]//g
:2,3s/[^1]//g
:3,4s/[^2]//g
:4,5s/[^3]//g
:5,6s/[^4]//g
:6,7s/[^5]//g
:7,8s/[^6]//g
:8,9s/[^7]//g
:9,10s/[^8]//g
:10,11s/[^9]//g
:%s/\n//g
:wq

Disassembly

gg<CR><NL>dd<CR><NL>10p<CR><NL>gg<CR><NL>dd<CR><NL>:1,2s/[^0]//g<CR><NL>:2,3s/[^1]//g<CR><NL>:3,4s/[^2]//g<CR><NL>:4,5s/[^3]//g<CR><NL>:5,6s/[^4]//g<CR><NL>:6,7s/[^5]//g<CR><NL>:7,8s/[^6]//g<CR><NL>:8,9s/[^7]//g<CR><NL>:9,10s/[^8]//g<CR><NL>:10,11s/[^9]//g<CR><NL>:%s/\n//g<CR><NL>:wq<CR><NL>

stdin

6235993855678680534502888327706445190111259763783753309249565337255475450407760221558439651350456009

stdout

88888888

stderr

strace