#include <bits/stdc++.h>
using namespace std;

int main() {
    int N;
    cin >> N;
    vector<int>a(21);
    for(int i = 0; i < N; i++) {
        int b;cin>>b;a[b]++;
    }
    long long ans1 = 1,ans2 = 1;
    for(int i = 1; i <= N; i++) {
        ans1 *= i;
        for(int j = 1; j <= a[i]; j++) {
            ans2 *= j;
        }
    }
    cout << ans1/ans2 << endl;
}