#include<cstdio>
#include<algorithm>
#include<string>
using namespace std;
bool comp(char lhs, char rhs) {
    if (lhs < rhs) {
        return true;
    } else {
        return false;
    }
}
int main() {
    char arr[21] ;
    while (scanf("%s", arr) != EOF) {
        string s = arr;
        sort(arr, arr + s.size(), comp);
        for (int i = 0 ; i < s.size(); ++i) {
            printf("%c", arr[i]);
        }
    }
}