#include <stdio.h>
#include <string.h>
int main(){
    char arr[21];
    while(scanf("%s", arr) != EOF){
        int len = strlen(arr);
        char temp;
        for (int i = 0; i < len; ++i) {
            for (int j = i+1; j < len; ++j) {
                if (arr[i] > arr[j]){
                    temp = arr[i];
                    arr[i] = arr[j];
                    arr[j] = temp;
                }
            }
        }
        printf("%s\n", arr);
    }
    return 0;
}