#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  int fre[26] = {0};
  for (int i = 0; i < n; i++) {
    fre[s[i] - 'a'] = fre[s[i] - 'a'] + 1;
  }
  string ans = "";
  for (int i = 0; i < 26; i++) {
    for (int j = 0; j < fre[i]; j++) {
      ans = ans + char(97 + i);
    }
  }
  cout << ans;
}
