#include <bits/stdc++.h>
using namespace std;
int freq[26];
int main() {
  int n;
  cin >> n;
  for (int i = 0; i < n; i++) {
    char c;
    cin >> c;
    freq[c - 'a']++;
  }
  for (int i = 0; i < 26; i++) {
    for (int j = 0; j < freq[i]; j++) cout << (char)('a' + i);
  }
}
