#include <bits/stdc++.h>
using namespace std;
template <typename T>
T ceil(T a, T b) {
  return (a + b - 1) / b;
}
template <typename T>
T gcd(T a, T b) {
  return b ? gcd(b, a % b) : a;
}
long long lcd(long long a, long long b) {
  if (a < b) {
    swap(a, b);
  }
  a /= gcd(a, b);
  return a * b;
}
template <typename T>
vector<T> allDivisors(T n) {
  vector<T> divisors;
  for (int i = 1; i <= sqrt(n); ++i) {
    if (n % i == 0) {
      divisors.push_back(i);
      if (n / i != i) {
        divisors.push_back(n / i);
      }
    }
  }
  return divisors;
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  int n;
  string str;
  map<char, int> mp;
  cin >> n >> str;
  for (char chr : str) {
    mp[chr]++;
  }
  for (pair<char, int> pa : mp) {
    char chr = pa.first;
    for (int i = 0; i < pa.second; ++i) {
      cout << chr;
    }
  }
  cout << "\n";
  return 0;
}
