#include <bits/stdc++.h>
#include <iostream>
#include <string>

using namespace std;

struct cmp{
    bool operator()(char& a, char& b){
        return a < b; //前面小后面大 升序
    }  
};

int main(){
    string str = "";
    getline(cin, str);

    sort(str.begin(), str.end(), cmp());
    
    cout << str << endl;
    
    return 0;
}