#include <bits/stdc++.h>
using namespace std;
int main() {
  string chaya, shaya;
  long long naa;
  ios::sync_with_stdio(0);
  cin.tie(NULL);
  chaya = "";
  cin >> naa;
  cin >> shaya;
  sort(shaya.begin(), shaya.end());
  cout << shaya;
  return 0;
}
