import math

MOD = 1000000007

m = input()

a = [1] * (m + 1)
b = [1] * (m + 1)
for i in xrange(1, m + 1):
    a[i] = a[i - 1] * i % MOD
    b[i] = pow(a[i], MOD - 2, MOD)
    
h = map(int, raw_input().split())
s = len(h)
sum = sum(h) + s - 1
if s == 1 and (h[0] == 0 or h[0] == m):
    print 1
elif m < sum:
    print "NA"
else:
    print a[s + m - sum] * b[s] * b[m - sum] % MOD