Kyoya Ootori has a bag with *n* colored balls that are colored with *k* different colors. The colors are labeled from 1 to *k*. Balls of the same color are indistinguishable. He draws balls from the bag one by one until the bag is empty. He noticed that he drew the last ball of color *i* before drawing the last ball of color *i* + 1 for all *i* from 1 to *k* - 1. Now he wonders how many different ways this can happen.
The first line of input will have one integer *k* (1 ≤ *k* ≤ 1000) the number of colors.

Then, *k* lines will follow. The *i*-th line will contain *c*<sub class="lower-index">*i*</sub>, the number of balls of the *i*-th color (1 ≤ *c*<sub class="lower-index">*i*</sub> ≤ 1000).

The total number of balls doesn't exceed 1000.
import sys 
import math
from math import *
from operator import add
from itertools import permutations 
import itertools
try:
	sys.stdin = open('input.txt', 'r') 
	sys.stdout = open('output.txt', 'w')
except noerror:
	print("no input_file")
inf = 1e10
mod = int(1e9 + 7)
def NcR(n, r):
	"""
    p holds the value of n*(n-1)*(n-2)...,
    k holds the value of r*(r-1)... 
    C(n, r) == C(n, n-r),
    choosing the smaller value """
	p = 1
	k = 1
	if (n - r < r):r = n - r
	if (r != 0):
		while (r):
			p *= n
			k *= r
			m = gcd(p, k)
			"""
			gcd of p, k
			dividing by gcd, to simplify product
			division by their gcd saves from the overflow"""
			p //= m
			k //= m
			n -= 1
			r -= 1
	return p
t=1;# t=int(input())
for _ in range(t):
	k=int(input())
	total=int(input())
	res=1
	for i in range(1,k):
		c=int(input())
		res = (res*NcR(total + c-1, c-1))%mod
		total+=c
	print(res)