vim, 21 bytes

Result

AC

Code [DL]

:s/./&\r/g|sor|%j!
ZZ

Disassembly

:s/./&\r/g|sor|%j!<NL>ZZ

stdin

9858449138822178359682376538986650882784917008061128891207048126832127137272631013212407965437316220

stdout

0000000001111111111111222222222222222333333333344444455555666666666777777777788888888888888889999999

stderr

strace