#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, i, j;
  cin >> n;
  string s;
  cin >> s;
  int a[26] = {0};
  for (i = 0; i < n; ++i) {
    a[int(s[i]) - int('a')]++;
  }
  for (i = 0; i < 26; ++i) {
    for (j = 0; j < a[i]; ++j) cout << char(97 + i);
  }
}
