# coding:UTF-8
import sys

MOD = 10 ** 9 + 7
INF = float('inf')


def extGcd(a, b):
    if b == 0:
        return [a, 1, 0]
    else:
        g, x, y = extGcd(b, a%b)
        return [g, int(y), int(x - (a // b) * y)]


def inv(a):
    r = extGcd(a, MOD)
    return r[1] % MOD


def comb(n, k):
    if n < k:
        return 0
    elif n < 0 or k < 0:
        return 0
    a = 1
    for i in range(k):
        a = a * (n - i) % MOD
    b = 1
    for i in range(1, k+1):
        b = b * i % MOD
    binv = inv(b)
    return (a * binv) % MOD


M = int(input())    # 数字
H = list(map(int, input().split()))     # スペース区切り連続数字
K = len(H)

if H[0] == 0:
    print("1")
    exit()

t = 0
for i in range(K):
    if i == K - 1:
        t += H[i]
    else:
        t += H[i] + 1

zan = M - t
res = comb(zan+K, K)

if res == 0:
    print("NA")
else:
    print("{}".format(res))