#include<cstdio>
#include<iostream>
#include<cmath>
#include<cstring>
#include<algorithm>
using namespace std;
const int SIZEN=1010,SIZEK=5010;
typedef long long LL;
const LL MOD=998244353;
int N;
int sum[SIZEN];
LL add[SIZEN][SIZEK]={0};
LL C(int x,int y)
{
	if(add[x][y]) return add[x][y];
	if(y==0) return 1;
	if(y==x) return 1;
	add[x][y]=(C(x-1,y-1)+C(x-1,y))%MOD;
	return add[x][y];
}
void read()
{
	scanf("%d",&N);
	for(int i=1;i<=N;i++) scanf("%d",&sum[i]);
}
void work()
{
	LL ans=1;
	int now=0;
	for(int i=1;i<=N;i++)
	{
		for(int j=1;j<=sum[i]-1;j++)
		{
			LL g=C(sum[i]-1,j-1);
			g%=MOD;
			g*=C(now+1,j);
			//cout<<g<<endl;
			g%=MOD;
			ans*=g;
			ans%=MOD;
			now+=sum[i];
		}
	}
	printf("%lld",ans);
}
int main()
{
	freopen("asm_formation.in","r",stdin);
	freopen("asm_formation.out","w",stdout);
	read();
	work();
	return 0;
}