#include <bits/stdc++.h>
using namespace std;
const int maxn = 100005;
vector<int> cnt;
string A;
int n;
int main() {
  cin >> n >> A;
  cnt.resize(26, 0);
  for (int i = 0; i < A.length(); i++) cnt[A[i] - 'a'] += 1;
  for (char i = 'a'; i <= 'z'; i++) {
    int c = cnt[i - 'a'];
    for (int j = 0; j < c; j++) cout << i;
  }
  cout << endl;
  return 0;
}
