#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<ll,ll>;
#define fix(x) fixed << setprecision(x)
#define asc(x) x, vector<x>, greater<x>
#define rep(i, n) for(ll i = 0; i < n; i++)
#define all(x) (x).begin(),(x).end()
template<class T>bool chmin(T&a, const T&b){if(a>b){a=b;return 1;}return 0;}
template<class T>bool chmax(T&a, const T&b){if(a<b){a=b;return 1;}return 0;}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    ll n, ans = 1, ans2 = 1;
    cin >> n;
    vector<ll> cnt(n,0);
    rep(i,n){
        int a;
        cin >> a;
        cnt[a-1]++;
    }
    ll m = n;
    rep(i,n){
        ans *= i+1;
        while(cnt[i]) ans2 *= cnt[i]--;
    }
    cout << ans/ans2 << '\n';
    return 0;
}