#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  vector<int> A(N);
  map<int, int> mp;
  for (int i = 0; i < N; i++) {
    cin >> A[i];
    mp[A[i]]++;
  }
  long long c = 1;
  for (auto i : mp) {
    while (i.second > 0) {
      c *= i.second;
      i.second--;
    }
  }
  long long ans = 1;
  for (int i = 1; i <= N; i++) {
    ans *= i;
  }
  cout << ans / c << endl;
}