#include <bits/stdc++.h>
using namespace std;
const int maxn = 100010;
long long gcd(long long x, long long y) {
  if (y == 0) return x;
  return gcd(y, x % y);
}
int main() {
  long long n;
  cin >> n;
  string s;
  cin >> s;
  vector<int> v(26);
  for (long long i = 0; i < n; i++) {
    v[s[i] - 'a']++;
  }
  for (long long i = 0; i < 26; i++) {
    while (v[i]--) {
      char c = i + 'a';
      cout << c;
    }
  }
  return 0;
}
