#include<bits/stdc++.h> 
using namespace std;
const int N=155;
int n, sum, d[N];
long long C[N][N];

int main()
{
    int n;scanf("%d", &n);
    int sum=0;
    for(int i=1;i<=n;i++)
    {
        scanf("%d", &d[i]); sum += d[i]-1;
        if(d[i]==0 && n>1) return printf("0\n"), 0;
    }
    if(n==1) return printf("%d\n", !d[1]), 0;
    if(sum!=(n-2)) return printf("0\n"), 0;
    
    for(int i=0;i<=n-2;i++)C[i][0] = 1; 
    for(int i=1;i<=n-2;i++)for(int j=1;j<=i;j++)
        C[i][j] = C[i-1][j-1] + C[i-1][j];
    long long ans=1;    
    for(int i=1;i<=n;i++)ans = ans * C[sum][d[i]-1], sum -= (d[i]-1);
    printf("%lld\n", ans);
    return 0;    
}

#include<bits/stdc++.h> 
using namespace std;
const int N=155;
int n,sum,d[N];
long long C[N][N];

int main()
{
	int n;scanf("%d", &n);
	int sum=0;
	for(int i=1;i<=n;i++)
	{
		scanf("%d",&d[i]),sum+=d[i]-1;
		if(d[i]==0 && n>1) return printf("0\n"), 0;
	}
	if(n==1) return printf("%d\n",!d[1]),0;
	if(sum!=(n-2)) return printf("0\n"), 0;
	
	for(int i=0;i<=n-2;i++)C[i][0] = 1; 
	for(int i=1;i<=n-2;i++)for(int j=1;j<=i;j++)
		C[i][j]=C[i-1][j-1]+C[i-1][j];
	long long ans=1;	
	for(int i=1;i<=n;i++)ans= ans*C[sum][d[i]-1],sum-=(d[i]-1);
	printf("%lld\n", ans);
	return 0;	
}