#include <bits/stdc++.h>
using namespace std;
char s[100000];
int a[100000];
int main() {
  int x;
  scanf("%d", &x);
  scanf("%s", s);
  int n = strlen(s);
  for (int i = 0; i < n; i++) a[i] = s[i];
  sort(a, a + n);
  for (int i = 0; i < n; i++) printf("%c", a[i]);
  printf("\n");
  return 0;
}
