#include <bits/stdc++.h>
using namespace std;
char str[100006];
int asc[128];
int main(void) {
  memset(asc, 0, sizeof(asc));
  int n;
  cin >> n >> str;
  for (int i = 0; i < n; i++) {
    asc[str[i]]++;
  }
  for (char i = 'a'; i <= 'z'; i++) {
    while (asc[i]) {
      asc[i]--;
      printf("%c", i);
    }
  }
  cout << endl;
  return 0;
}
