#include <stdio.h>
#define mod 1000000007

int c[1005][1005], a[1005];
int main()
{
	int k, sum;
	scanf("%d", &k);
	for (int i = 0; i < k; i++)
	{
		scanf("%d", &a[i]);
		sum += a[i];
	}
	c[0][0] = 1;
	for (int i = 1; i <= sum; i++)
	{
		c[i][0] = 1;
		for (int j = 1; j <= i; j++)
		{
			c[i][j] = (c[i - 1][j] + c[i - 1][j - 1]) % mod;
		}
	}
	long long res = 1, cur = 0;
	for (int i = 0; i < k; i++)
	{
		res = res * c[cur + a[i] - 1][a[i] - 1] % mod;
		cur += a[i];
	}
	printf("%lld", res);
	return 0;
}