M = int(input())
H = list(map(int, input().split()))
K = len(H)
S = sum(H)
mod = int(1e9) + 7

maxf = M - S + 1 # <-- input factional limitation

def doubling(n, m):
    y = 1
    base = n
    tmp = m
    while tmp != 0:
        if tmp % 2 == 1:
            y *= base
            y %= mod
        base *= base
        base %= mod
        tmp //= 2
    return y

def inved(a):
    x, y, u, v, k, l = 1, 0, 0, 1, a, mod
    while l != 0:
        x, y, u, v = u, v, x - u * (k // l), y - v * (k // l)
        k, l = l, k % l
    return x % mod

fact = [1 for _ in range(maxf+1)]
invf = [1 for _ in range(maxf+1)]

for i in range(maxf):
    fact[i+1] = (fact[i] * (i+1)) % mod
invf[-1] = inved(fact[-1])
for i in range(maxf, 0, -1):
    invf[i-1] = (invf[i] * i) % mod

if H == [0]:
    print(1)
else:
    if S + K - 1 > M:
        print("NA")
    else:
        print((fact[M-S+1] * invf[K] * invf[M-S-K+1]) % mod)