#include <iostream>
#include <algorithm>
using namespace std;

bool cmp(char a,char b){
    return a < b;
}

int main() {
    string str;
    cin >> str;

    int len = str.length();
    char* s = new char[len];
    for(int i = 0;i < len; i++){
        s[i] = str[i];
    }

    sort(s, s + len, cmp);

    puts(s);
    return 0;

}