c-gcc, 77 bytes

Result

WA

Code [DL]

f(char*a){return*a-*1[&a];}s[100];main(){gets(s);qsort(s,100,1,f);puts(s);}

stdin

1639654158911885768941045217241611045345579916310969559900812218689902742171101122113869720932702469

stdout

9642072390279683112211011712472099868122180099559690136199755435401161427125401498675881198514569361

stderr

/volume/CODE.c:1:1: warning: return type defaults to ‘int’ [-Wimplicit-int]
 f(char*a){return*a-*1[&a];}s[100];main(){gets(s);qsort(s,100,1,f);puts(s);}
 ^
/volume/CODE.c:1:28: warning: data definition has no type or storage class
 f(char*a){return*a-*1[&a];}s[100];main(){gets(s);qsort(s,100,1,f);puts(s);}
                            ^
/volume/CODE.c:1:28: warning: type defaults to ‘int’ in declaration of ‘s’ [-Wimplicit-int]
/volume/CODE.c:1:35: warning: return type defaults to ‘int’ [-Wimplicit-int]
 f(char*a){return*a-*1[&a];}s[100];main(){gets(s);qsort(s,100,1,f);puts(s);}
                                   ^
/volume/CODE.c: In function ‘main’:
/volume/CODE.c:1:42: warning: implicit declaration of function ‘gets’ [-Wimplicit-function-declaration]
 f(char*a){return*a-*1[&a];}s[100];main(){gets(s);qsort(s,100,1,f);puts(s);}
                                          ^
/volume/CODE.c:1:50: warning: implicit declaration of function ‘qsort’ [-Wimplicit-function-declaration]
 f(char*a){return*a-*1[&a];}s[100];main(){gets(s);qsort(s,100,1,f);puts(s);}
                                                  ^
/volume/CODE.c:1:67: warning: implicit declaration of function ‘puts’ [-Wimplicit-function-declaration]
 f(char*a){return*a-*1[&a];}s[100];main(){gets(s);qsort(s,100,1,f);puts(s);}
                                                                   ^
/tmp/ccpQeipW.o: In function `main':
CODE.c:(.text.startup+0xc): warning: the `gets' function is dangerous and should not be used.

strace