#include<cstdio>
#include<vector>
#include<iostream>
#include<cstring>
#include<algorithm>
#include<queue>
using namespace std;
int n,sum,ans;
int num1[100100];
int num[100100];
int dui[500100];
void dfs(int i,int k)
{
	num1[i]--;
	dui[k]=i;
	if (num1[i]==0)
	{
		int v=i;
		for (int j=k;j>=1;j--)
		 {
		 	if (v<dui[j]&&num1[dui[j]]==0)
		 	 return;
		 }
	}
	if (k==sum) ans++;
	for (int j=1;j<=n;j++)
	{
		if (num1[j]>0)
		{
			dfs(j,k+1);
			num1[j]++;
			dui[k+1]=0;
		}

	}
}
int main()
{
	freopen("asm_formation.in","r",stdin);
	freopen("asm_formation.out","w",stdout);
	cin>>n;
	for (int i=1;i<=n;i++)
	{
	 cin>>num[i];
     sum+=num[i];
	}
	for (int i=1;i<=n;i++)
	{
		for (int j=1;j<=sum;j++)
		 dui[j]=0;
		for (int j=1;j<=n;j++)
		 num1[j]=num[j];
	    dfs(i,1);
    }
	cout<<ans;
	return 0;
}