#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  while (scanf("%d", &n) == 1) {
    vector<int> cnt(30, 0);
    for (int i = 0; i < n; i++) {
      char ch;
      cin >> ch;
      cnt[ch - 'a']++;
    }
    for (int i = 0; i < 26; i++)
      for (int j = 1; j <= cnt[i]; j++) {
        char ch = i + 'a';
        cout << ch;
      }
    cout << endl;
  }
  return 0;
}
