#include <bits/stdc++.h>
using namespace std;
void __print(int x) { cout << x; }
void __print(long x) { cout << x; }
void __print(long long x) { cout << x; }
void __print(unsigned x) { cout << x; }
void __print(unsigned long x) { cout << x; }
void __print(unsigned long long x) { cout << x; }
void __print(float x) { cout << x; }
void __print(double x) { cout << x; }
void __print(long double x) { cout << x; }
void __print(char x) { cout << '\'' << x << '\''; }
void __print(const char *x) { cout << '\"' << x << '\"'; }
void __print(const string &x) { cout << '\"' << x << '\"'; }
void __print(bool x) { cout << (x ? "true" : "false"); }
void _print() { cout << "]\n"; }
template <typename T, typename... V>
void _print(T t, V... v) {
  __print(t);
  if (sizeof...(v)) cout << ", ";
  _print(v...);
}
const long long int dx4[4] = {+1, -1, 0, 0};
const long long int dy4[4] = {0, 0, +1, -1};
const long long int dx8[8] = {-1, -1, -1, 0, 0, 1, 1, 1};
const long long int dy8[8] = {-1, 0, 1, -1, 1, -1, 0, 1};
const long long int MOD = 1e9 + 7;
const long long int INF = 1e10;
const long long int N = 2e5 + 5;
void solve() {
  long long int n;
  string s;
  cin >> n >> s;
  map<char, long long int> cnt;
  for (auto x : s) cnt[x]++;
  for (auto x : cnt)
    while (x.second) cout << x.first, x.second--;
  return;
}
int32_t main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long int t = 1;
  while (t--) solve();
  return 0;
}
