/**
 *   @FileName	a.cpp
 *   @Author	kanpurin
 *   @Created	2022.04.16 00:39:29
**/

#include "bits/stdc++.h" 
using namespace std; 
typedef long long ll;


int main() {
    int n;cin >> n;
    vector<int> cnt(20);
    vector<ll> fact(21);
    fact[0] = 1;
    for (int i = 0; i < 20; i++) {
        fact[i+1] = fact[i]*(i+1);
    }
    for (int i = 0; i < n; i++) {
        int a;cin >> a;
        cnt[a-1]++;
    }
    ll ans = fact[n];
    for (int i = 0; i < 20; i++) {
        ans /= fact[cnt[i]];
    }
    cout << ans << endl;
    return 0;
}