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.
'''
    Auther: ghoshashis545 Ashis Ghosh
    College: jalpaiguri Govt Enggineering College

'''
from os import path
from io import BytesIO, IOBase
import sys
from heapq import heappush,heappop
from functools import cmp_to_key as ctk
from collections import deque,Counter,defaultdict as dd 
from bisect import bisect,bisect_left,bisect_right,insort,insort_left,insort_right
from itertools import permutations
from datetime import datetime
from math import ceil,sqrt,log,gcd
def ii():return int(input())
def si():return input().rstrip()
def mi():return map(int,input().split())
def li():return list(mi())
abc='abcdefghijklmnopqrstuvwxyz'
mod=1000000007
#mod=998244353
inf = float("inf")
vow=['a','e','i','o','u']
dx,dy=[-1,1,0,0],[0,0,1,-1]

def bo(i):
    return ord(i)-ord('0')

file = 1
def ceil(a,b):
    return (a+b-1)//b




def solve():


    # for _ in range(ii()):
    N = 10001
    invfact = [0]*N
    fact = [1]*N
    for i in range(1,N):
        fact[i] = (fact[i-1]*i)%mod
    invfact[-1] = pow(fact[-1],mod-2,mod)
    for i in range(N-2,-1,-1):
        invfact[i] = ((i+1)*invfact[i+1])%mod

    def nCr(x,y):
        if y > x:
            return 0
        ans = (invfact[x-y]*invfact[y])%mod
        ans *= fact[x]
        ans %= mod
        return ans

    k = ii()
    ans = 1
    cnt = ii()
    for i in range(1,k):
        x = ii()
        cnt += (x-1)
        ans *= nCr(cnt,x-1)
        ans %= mod
        cnt += 1
    print(ans)








            





    
        








        
if __name__ =="__main__":

    if(file):

        if path.exists('tmp/input.txt'):
            sys.stdin=open('tmp/input.txt', 'r')
            sys.stdout=open('tmp/output.txt','w')
        else:
            input=sys.stdin.readline
    solve()
