#include <bits/stdc++.h>
using namespace std;
int N, base[200010], i, j;
char A[200010];
int main() {
  cin >> N;
  cin >> A;
  for (i = 1; i <= N; ++i) base[i] = A[i - 1] - 'a';
  sort(base + 1, base + N + 1);
  for (i = 1; i <= N; ++i) cout << (char)(base[i] + 'a');
}
