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

int main() {
    int n; cin >> n;
    vector<ll> a(n), cnt(n + 1, 0);
    ll ans = 1;
    for (int i=0; i<n; i++) {
        cin >> a[i];
        ans *= i + 1;
        cnt[a[i]]++;
    }

    for (int i=0; i<n; i++) {
        for (int j=1; j<=cnt[i]; j++) ans /= j;
    }

    cout << ans << "\n";

}