#include <bits/stdc++.h>
using namespace std;
void re(int &x) {
  x = 0;
  char ch = getchar();
  int b = 0;
  while (ch < '0' || ch > '9') {
    if (ch == '-') b = 1;
    ch = getchar();
  }
  while (ch >= '0' && ch <= '9') {
    x = (x << 1) + (x << 3) + ch - '0';
    ch = getchar();
  }
  if (b == 1) x *= -1;
}
int n;
char a[110000], b[30][110000];
int s[110000], vis[110000];
int main() {
  re(n);
  scanf("%s", a + 1);
  for (register int i = 1; i <= n; i++) {
    vis[a[i] - 'a' + 1]++;
  }
  char m = 'a';
  for (register int i = 1; i <= 30; i++, m++) {
    if (!vis[i]) continue;
    for (register int j = 1; j <= vis[i]; j++) cout << m;
  }
  return 0;
}
