#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  string s;
  cin >> s;
  vector<int> cnt(26);
  for (char c : s) ++cnt[c - 'a'];
  for (int i = 0; i < 26; ++i)
    for (int j = 0; j < cnt[i]; ++j) cout << char('a' + i);
  cout << '\n';
}
