#include <bits/stdc++.h>
using namespace std;
int expo(int n, int k) {
  if (k == 0) return 1;
  if (k == 1) return n;
  int res = expo(n, k >> 1);
  if (k % 2) return res * res * n;
  return res * res;
}
int cnt[26];
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  ;
  int n;
  cin >> n;
  string s;
  cin >> s;
  for (int i = 0; i < n; ++i) {
    int id = (int)s[i] - (int)'a';
    cnt[id]++;
  }
  string first = "";
  for (int i = 0; i < 26; ++i) {
    if (cnt[i] == 0) continue;
    char ch = 'a' + i;
    for (int j = 0; j < cnt[i]; ++j) {
      first += ch;
    }
  }
  cout << first << endl;
}
