#include <bits/stdc++.h>
#pragma GCC optimize("O3")
template <class t = int>
t get() {
  t a;
  std::cin >> a;
  return a;
}
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  cerr.tie(NULL);
  ;
  int n;
  cin >> n;
  vector<int> a(26);
  for (__typeof(0) c = 0; c < n; c++) {
    a[get<char>() - 'a']++;
  }
  for (unsigned int c = 0; c < a.size(); cerr << a[c++] << ' ')
    ;
  cerr << endl;
  ;
  for (__typeof(0) c = 0; c < 26; c++) {
    if (a[c]) {
      while (a[c] > 0) {
        cout << (char)(c + 'a');
        a[c]--;
      }
    }
  }
}
