bash-pure, 104 bytes

Result

WA

Code [DL]

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

stdin

2390302451898386743708499195315447367810118293750893990230793960117394567400638936104138300577235052

stdout

stderr

/bin/bash: warning: setlocale: LC_ALL: cannot change locale (en_US.UTF-8)
/code.bash: line 3: ${0..a[i]}: bad substitution

strace