bash-pure, 85 bytes

Result

WA

Code [DL]

while read -n 1 c;do a[c]=${a[c]}@;done
for i in {0..9};do echo -n ${a[c]//@/$i};done

stdin

0305505819098705426818049885678996324770493207851686419626498252948497447157014368575598394734423716

stdout

000000000111111111222222222333333333444444444555555555666666666777777777888888888999999999

stderr

/bin/bash: warning: setlocale: LC_ALL: cannot change locale (en_US.UTF-8)

strace