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
#sys.setrecursionlimit(20000)
#from collections import deque #Counter
#from itertools import accumulate, product
#from functools import reduce
#from math import gcd #sqrt
import math


def rall():
    return [x.strip() for x in sys.stdin.readlines()]
def rl():
    return sys.stdin.readline().strip()
def rl_types(types):
    str_list = [x for x in sys.stdin.readline().strip().split(' ')]
    return [types[i](str_list[i]) for i in range(len(str_list))]

def pr( something='' ):
    sys.stdout.write( str(something) + '\n')
def pra( array ):
    sys.stdout.write( ' '.join([str(x) for x in array]) + '\n')



if __name__ == '__main__':

    K = int( rl() )
    colors = [int(rl()) for _ in range(K)]
    #pra(colors)

    MOD = 1_000_000_007
    nways = 1
    placed = colors[0] # place all the ones first
    for i in range(1,K):
        boxes = placed+1
        toplace = colors[i]-1 # -1 because of the one that was already placed
        nways = (nways * math.comb((boxes+toplace-1),toplace)) % MOD
        placed += colors[i]
    print(nways)


