#include<bits/stdc++.h>
using namespace std;
int n,cnt,tot=1;
int c[205][205],a[205];
int main(){
	freopen("ctree.in","r",stdin);
	freopen("ctree.out","w",stdout);
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	cin>>n;
	if(n==1){
		cin>>cnt;
		if(cnt==0){
			cout<<1<<endl;
			return 0;
		}
		cout<<0<<endl;
		return 0;
	}
	for(int i=0;i<=n;i++){
		c[i][0]=1;
		for(int j=1;j<=i;j++){
			c[i][j]=c[i-1][j]+c[i-1][j-1];
		}
	}
	for(int i=1;i<=n;i++){
		cin>>a[i];
		if(a[i]==0){
			cout<<0<<endl;
			return 0;
		}
		a[i]-=1;
		cnt+=a[i];
	}
	if(cnt!=n-2){
		cout<<0<<endl;
		return 0;
	}
	cnt=0;
	for(int i=1;i<=n;i++){
		tot*=c[n-2-cnt][a[i]];
		cnt+=a[i];
	}
	cout<<tot<<endl;
	return 0;
}