#include <bits/stdc++.h>
using namespace std;
int res[100000 + 10];
int main() {
  int n;
  string s;
  cin >> n;
  cin >> s;
  for (int i = 0; i < n; i++) res[i] = s[i] - 'a';
  sort(res, res + n);
  for (int i = 0; i < n; i++) {
    char ch = res[i] + 'a';
    cout << ch;
  }
  return 0;
}
