#include<cstdio>
long long s[4001][5001]={0};
int p[1001]={0};
int main()
{
	freopen("asm_formation.in","r",stdin);
	freopen("asm_formation.out","w",stdout);
	for (int i=1;i<=4000;i++) s[i][1]=1;
	for (int i=1;i<=5000;i++) s[1][i]=i;
	for (int i=1;i<=5000;i++) s[0][i]=1;
		for (int i=2;i<=4000;i++)
		for (int j=2;j<=5000;j++)
			s[i][j]=(s[i-1][j]+s[i][j-1])% 998244353;
	int n;
	long long sum=0,ans=1;
	scanf("%d",&n);
	for (int i=1;i<=n;i++)
		scanf("%d",&p[i]);
	sum=p[1];
	for (int i=2;i<=n;i++)
	{
		ans=(ans*s[p[i]-1][sum+1])% 998244353;
		sum+=p[i];
	}
	printf("%lld",ans);
}