#include <bits/stdc++.h>
using namespace std;
template <typename T>
int countDigit(T n) {
  if (n < 0) n *= -1;
  return floor(log10(n) + 1);
}
template <typename T>
T gcd(T a, T b) {
  return b ? gcd(b, a % b) : a;
}
template <typename T>
T lcm(T a, T b) {
  return a * b / gcd(a, b);
}
void fastscan(int &x) {
  bool neg = false;
  register int c;
  x = 0;
  c = getchar();
  if (c == '-') {
    neg = true;
    c = getchar();
  }
  for (; (c > 47 && c < 58); c = getchar()) x = (x << 1) + (x << 3) + c - 48;
  if (neg) x *= -1;
}
int main() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  map<char, int> m;
  for (int i = 0; i < s.size(); i++) m[s[i]]++;
  for (auto x : m) {
    while (x.second) {
      cout << x.first;
      x.second--;
    }
  }
  return 0;
}
