#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  int arr[26];
  for (int i = 0; i < 26; i++) {
    arr[i] = 0;
  }
  for (int i = 0; i < n; i++) {
    arr[s[i] - 'a']++;
  }
  vector<char> ans;
  for (int i = 0; i < 26; i++) {
    while (arr[i] != 0) {
      ans.push_back((char)(i + 'a'));
      arr[i]--;
    }
  }
  for (int i = 0; i < ans.size(); i++) {
    cout << ans[i];
  }
  return 0;
}
