#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 5;
long long int cnt[26];
void solve() {
  string s;
  long long int n;
  cin >> n >> s;
  for (char i : s) cnt[i - 'a']++;
  for (long long int i = 0; i < 26; i++)
    for (long long int j = 0; j < cnt[i]; j++) cout << (char)(i + 'a');
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long int T = 1;
  while (T--) solve();
  return 0;
}
