bash-pure, 91 bytes

Result

WA

Code [DL]

while read -n 1 c;do((a[c]++));done
for i in {0..9};do while a[i]--;do echo -n $i;done;done

stdin

9856602865473023851390834403287725955026108510761992825582020068664456251131395879228081762188136319

stdout

stderr

/bin/bash: warning: setlocale: LC_ALL: cannot change locale (en_US.UTF-8)
/code.bash: line 2: a[i]--: command not found
/code.bash: line 2: a[i]--: command not found
/code.bash: line 2: a[i]--: command not found
/code.bash: line 2: a[i]--: command not found
/code.bash: line 2: a[i]--: command not found
/code.bash: line 2: a[i]--: command not found
/code.bash: line 2: a[i]--: command not found
/code.bash: line 2: a[i]--: command not found
/code.bash: line 2: a[i]--: command not found
/code.bash: line 2: a[i]--: command not found

strace