php, 52 bytes

Result

WA

Code [DL]

<? $a=str_split(fgets(STDIN));sort($a)?><?=join($a);

stdin

3768677679246232610700949883194498451356761601006345457390397104566859872835175355700816927879993480

stdout

<? $a=str_split(fgets(STDIN));sort($a)?>

stderr

PHP Notice:  Undefined variable: a in /volume/CODE on line 1
PHP Warning:  join(): Argument must be an array in /volume/CODE on line 1

strace