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

4643876103826507467114135787096961805077420196635463169702876119191945982246717096459797110358010869

stdout

stderr

strace