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