#include <bits/stdc++.h>
using namespace std;
const int nmax = 1e5 + 42;
string inp;
int n;
int seen[26];
int main() {
  cin >> n;
  cin >> inp;
  for (auto k : inp) seen[k - 'a']++;
  for (int i = 0; i < 26; i++)
    for (int j = 0; j < seen[i]; j++) cout << char(i + 'a');
  cout << endl;
  return 0;
}
