#include <bits/stdc++.h>
int main() {
  int n;
  std::cin >> n;
  char c;
  int a[26] = {0};
  for (int i = 0; i < n; ++i) {
    std::cin >> c;
    a[c - 'a'] += 1;
  }
  for (int i = 0; i < 26; ++i) {
    for (int j = 0; j < a[i]; j++) {
      std::cout << char('a' + i);
    }
  }
  std::cout << std::endl;
  return 0;
}
