#include <bits/stdc++.h>
using namespace std;
int n, b[30];
int main() {
  char a[100000];
  while (~scanf("%d", &n)) {
    scanf("%s", a);
    memset(b, 0, sizeof(b));
    for (int i = 0; i < n; i++) {
      b[a[i] - 'a']++;
    }
    for (int i = 0; i < 26; i++) {
      while (b[i]) {
        printf("%c", i + 'a');
        b[i]--;
      }
    }
    printf("\n");
  }
}
