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