#include <bits/stdc++.h>
using namespace std;
const int MAX_CHAR = 26;
void sortString(string &str) {
  int charCount[MAX_CHAR] = {0};
  for (int i = 0; i < str.length(); i++) charCount[str[i] - 'a']++;
  for (int i = 0; i < MAX_CHAR; i++)
    for (int j = 0; j < charCount[i]; j++) cout << (char)('a' + i);
}
int main() {
  int n;
  string s;
  cin >> n >> s;
  sortString(s);
  return 0;
}
