c-gcc, 107 bytes

Result

WA

Code [DL]

char c,s[1],i=100;main(){while(i--){read(0,&c,1);s[c-48]++;}for(;i<10;i++){while(s[i]--)printf("%d",i);}}

stdin

2913126110783029830971696584350956859920968294822190207350446348231503554260759582186571043035034016

stdout

-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-10000000000000011111111112222222222233333333333444444445555555555556666666667777788888888899999999999

stderr

/volume/CODE.c:1:19: warning: return type defaults to ‘int’ [-Wimplicit-int]
 char c,s[1],i=100;main(){while(i--){read(0,&c,1);s[c-48]++;}for(;i<10;i++){while(s[i]--)printf("%d",i);}}
                   ^
/volume/CODE.c: In function ‘main’:
/volume/CODE.c:1:37: warning: implicit declaration of function ‘read’ [-Wimplicit-function-declaration]
 char c,s[1],i=100;main(){while(i--){read(0,&c,1);s[c-48]++;}for(;i<10;i++){while(s[i]--)printf("%d",i);}}
                                     ^
/volume/CODE.c:1:83: warning: array subscript has type ‘char’ [-Wchar-subscripts]
 char c,s[1],i=100;main(){while(i--){read(0,&c,1);s[c-48]++;}for(;i<10;i++){while(s[i]--)printf("%d",i);}}
                                                                                   ^
/volume/CODE.c:1:89: warning: implicit declaration of function ‘printf’ [-Wimplicit-function-declaration]
 char c,s[1],i=100;main(){while(i--){read(0,&c,1);s[c-48]++;}for(;i<10;i++){while(s[i]--)printf("%d",i);}}
                                                                                         ^
/volume/CODE.c:1:89: warning: incompatible implicit declaration of built-in function ‘printf’
/volume/CODE.c:1:89: note: include ‘<stdio.h>’ or provide a declaration of ‘printf’

strace