#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 5;
const int inf = 1e9 + 1;
const int prime_100000000 = 5761460;
const double eps = 1e-15;
const double EPS = 1e-9;
const double PI = acos(-1.0);
long long powmod(long long a, long long b, long long MOD) {
  long long ans = 1;
  while (b) {
    if (b % 2) ans = ans * a % MOD;
    a = a * a % MOD;
    b /= 2;
  }
  return ans;
}
long long GCD(long long x, long long y) {
  if (x % y == 0)
    return y;
  else
    return (GCD(y, x % y));
}
const long long mod = 1e9 + 7;
int main() {
  int n;
  string s;
  while (cin >> n) {
    cin >> s;
    int a[28];
    for (int i = 0; i < 26; i++) {
      a[i] = 0;
    }
    for (int i = 0; i < n; i++) {
      a[s[i] - 'a']++;
    }
    string ss = "";
    for (int i = 0; i < 26; i++) {
      for (int j = 0; j < a[i]; j++) {
        ss += ('a' + i);
      }
    }
    cout << ss << endl;
  }
  return 0;
}
