from math import comb

MOD = 10 ** 9 + 7

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)