MOD = 10 ** 9 + 7
modinv = lambda a, mod=MOD: pow(a, -1, mod)


def comb(N, K, mod=MOD):
    ret = 1
    for i in range(K):
        ret = ret * (N - i) * modinv(1 + i) % mod
    return ret


M = int(input())
H = list(map(int, input().split()))
if H == [0]:
    print(1)
    exit()

L = len(H)
W = M - sum(H)
if W < L - 1:
    print('NA')
    exit()
print(comb(W + 1, L) % MOD)