d-gdc, 114 bytes

Result

ERROR

Code [DL]

import std.stdio;import std.array;import std.algorithm;void main(){write(join(sort!("a<b")(split(readln(),""))));}

stdin

5673095204578093225800825390313393474003548016050482356437011676932937592383969171187453227374514110

stdout

stderr

strace