#include <iostream>
#include <vector>
#include <cmath>
#include <map>
#include <set>
#include <iomanip>
#include <queue>
#include <algorithm>
#include <numeric>
#include <deque>

using namespace std;

vector<vector<long long>> comb;

void combinations(long long n, long long modc=4e18){
    comb.resize(n+1);
    for (long long i=0; i<=n; i++){
        comb[i].resize(n+1);
        comb[i][0] = 1;
    }

    for (long long i=1; i <= n; i++){
        for (long long j=1; j <= i; j++){
            comb[i][j] = (comb[i-1][j-1] + comb[i-1][j]) % modc;
        }
    }
}

int main(){

    combinations(100);

    long long N, A, M, ans=1;
    cin >> N;
    M = N;
    vector<long long> cnt(N);
    for (int i=0; i<N; i++){
        cin >> A; A--;
        cnt[A]++;
    }

    for (int j=0; j<N; j++){
        ans *= comb[M][cnt[j]];
        M -= cnt[j];
    }

    cout << ans << endl;

    
    return 0;
}