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