c-gcc, 99 bytes

Result

WA

Code [DL]

char s[1],i=100;main(){for(;i--;s[*s]++)read(0,&s,1);for(;58-i++;){for(;s[i]--;write(1,&i,1));};}

stdin

7429547504836265698290566869725394959370045641595683541255215771586599446054446209755844887266193061

stdout

0000000111111222222223333344444444444444555555555555555555666666666666667777777788888888999999999999

stderr

/volume/CODE.c:1:17: warning: return type defaults to ‘int’ [-Wimplicit-int]
 char s[1],i=100;main(){for(;i--;s[*s]++)read(0,&s,1);for(;58-i++;){for(;s[i]--;write(1,&i,1));};}
                 ^
/volume/CODE.c: In function ‘main’:
/volume/CODE.c:1:34: warning: array subscript has type ‘char’ [-Wchar-subscripts]
 char s[1],i=100;main(){for(;i--;s[*s]++)read(0,&s,1);for(;58-i++;){for(;s[i]--;write(1,&i,1));};}
                                  ^
/volume/CODE.c:1:41: warning: implicit declaration of function ‘read’ [-Wimplicit-function-declaration]
 char s[1],i=100;main(){for(;i--;s[*s]++)read(0,&s,1);for(;58-i++;){for(;s[i]--;write(1,&i,1));};}
                                         ^
/volume/CODE.c:1:74: warning: array subscript has type ‘char’ [-Wchar-subscripts]
 char s[1],i=100;main(){for(;i--;s[*s]++)read(0,&s,1);for(;58-i++;){for(;s[i]--;write(1,&i,1));};}
                                                                          ^
/volume/CODE.c:1:80: warning: implicit declaration of function ‘write’ [-Wimplicit-function-declaration]
 char s[1],i=100;main(){for(;i--;s[*s]++)read(0,&s,1);for(;58-i++;){for(;s[i]--;write(1,&i,1));};}
                                                                                ^

strace