#include <bits/stdc++.h>
using namespace std;
long long int power(long long int a, long long int b) {
  long long int ans = 1;
  while (b > 0) {
    if (b & 1) ans = (ans * a);
    b = b >> 1;
    a = (a * a);
  }
  return ans;
}
long long int modInverse(long long int n, long long int m,
                         long long int mod = 1000000007) {
  return power(n, m - 2) % mod;
}
bool prime(long long int n) {
  if (n == 0 || n == 1) return 0;
  for (long long int i = 2; i * i <= n; i++)
    if (n % i == 0) return 0;
  return 1;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long int n;
  cin >> n;
  string s;
  cin >> s;
  long long int a[26] = {};
  for (long long int i = 0; i < n; i++) a[s[i] - 'a']++;
  string ans = "";
  for (long long int i = 0; i < 26; i++) {
    for (long long int j = 0; j < a[i]; j++) ans += (i + 'a');
  }
  cout << ans << endl;
  return 0;
}
