#include <bits/stdc++.h>
using namespace std;
vector<char> a;
int main() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  for (int i = 0; i < n; i++) {
    a.push_back(s[i]);
  }
  sort(a.begin(), a.end());
  for (int i = 0; i < n; i++) {
    cout << a[i];
  }
  cout << endl;
}
