#include <bits/stdc++.h>

using namespace std;
using LL = long long;

int main(){
    int N;
    cin >> N;
    vector<int> A(N);
    for(int i = 0; i < N; i++) cin >> A[i];
    sort(A.begin(), A.end());
    A.emplace_back(100);
    vector<LL> fact(25);
    fact[1] = 1;
    for(int i = 1; i < 20; i++) fact[i+1] = fact[i] * (i + 1);
    LL ans = fact[N];
    int cnt = 1;
    for(int i = 0; i < N; i++){
        if(A[i+1] == A[i]) cnt++;
        else{
            ans /= fact[cnt];
            cnt = 1;
        }
    }
    cout << ans << endl;
}