#include <bits/stdc++.h>
using namespace std;
const int N = 1e3 + 2;
int a[N], b[N][N], dr[8] = {1, 1, 0, -1, -1, -1, 0, 1},
                   dc[8] = {0, 1, 1, 1, 0, -1, -1, -1};
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int n;
  string s;
  cin >> n >> s;
  for (int i = 0; i < (int)n; i++) a[s[i] - 'a']++;
  deque<char> q;
  string s1, s2;
  for (int i = 0; i < (int)26; i++)
    for (int j = 0; j < (int)a[i]; j++) s1 += 'a' + i;
  cout << s1 << '\n';
}
