#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <iomanip>
#include <cmath>
#include <stdio.h>
#include <queue>
#include <deque>
#include <cstdio>
#include <set>
#include <map>
#include <bitset>
#include <stack>
#include <cctype>
using namespace std;
int a[22];
int main() {
	long long n, ans = 1;
	cin >> n;
	for (long long i = 0; i < n; i++) {
		cin >> a[i];
		ans *= i + 1;
	}
	sort(a, a + n);
	long long co = 0;
	for (int i = 0; i < n; i++) {
		if (i != 0 && a[i] != a[i - 1]) {
			for (long long j = 2; j <= co; j++) {
				ans /= j;
			}
			co = 0;
		}
		co++;
	}
	cout << ans << endl;
}