#include <bits/stdc++.h>
using namespace std;
struct coun {
  char fig;
  int num;
  coun() { num = 0; }
} figure[30];
bool cmp(coun a, coun b) {
  if (a.num == b.num) return a.fig < b.fig;
  return a.num > b.num;
}
int cnt[300];
int main() {
  int n;
  while (cin >> n) {
    string str;
    cin >> str;
    memset(cnt, 0, sizeof(cnt));
    int len = str.size();
    for (int i = 0; i <= len - 1; i++) {
      cnt[str[i]]++;
    }
    string ans = "";
    for (char i = 'a'; i <= 'z'; i++) {
      int tmp = cnt[i];
      while (tmp--) {
        ans += i;
      }
    }
    cout << ans << endl;
  }
}
