#include<iostream>
#include <set>
#include<string>
using namespace std;
int main() {
    string num;
    cin >> num;
    string s;
    cin>>s;
    int freq[26]{};
   for (char i : s) freq[i-'a']++;
   for (int  i = 0; i < 26; i++) {
       while (freq[i]>0){
           cout << char(i+'a');
       freq[i]--;
   }
   }
}