#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=0;i<n;i++)
#define rng(i,x,n) for(int i=x;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define fi first
#define se second
#define pb push_back
#define sz(a) (int)a.size()
#define vec(...) vector<__VA_ARGS__>
#define _3rfKJyA ios::sync_with_stdio(0),cin.tie(0)
typedef long long ll;
using pii=pair<int,int>;
using vi=vector<int>;
void print(){cout<<'\n';}
template<class h,class...t>
void print(const h&v,const t&...u){cout<<v<<' ',print(u...);}
// e

using ld=long double;

signed main(){
_3rfKJyA;
	int n;
	cin>>n;
	vi cnt(n+1,0);
	rep(i,n){
		int x;cin>>x;
		cnt[x]+=1;
	}
	ll ans=1;
	for(ll i=1;i<=n;i++){
		ans*=i;
	}
	rng(i,1,n+1){
		ll e=1;
		rep(j,cnt[i]){
			e*=(j+1);
		}
		ans/=e;
	}
	cout<<ans<<"\n";
//	
	return 0;
}