#include <bits/stdc++.h>
using namespace std;
const int N = 2 * 1e5 + 10;
const long long inf = 1e18 + 100;
const long long mod = 1e9 + 7;
void solve() {
  long long n;
  cin >> n;
  string s;
  cin >> s;
  long long arr[26] = {0};
  for (int i = 0; i < n; i++) {
    arr[s[i] - 'a']++;
  }
  string odd = "", ans = "", ws = "";
  for (int i = 0; i < 26; i++) {
    char ch = i + 'a';
    for (int j = 0; j < arr[i]; j++) {
      cout << ch;
    }
  }
}
int main() {
  std::ios::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long t = 1;
  while (t--) {
    solve();
  }
  return 0;
}
