M = input()
H = map(int, raw_input().split())
H = filter(lambda x: x > 0, H)

ans = 0
mod = int(1e+9 + 7)
fact = [0] * (10**6 + 10)
fact[0] = 1

S = sum(H)
n = len(H)


def powmod(x, p):
  res = 1
  tmp = x
  while p > 0:
    if p & 1:
      res *= tmp
      res %= mod
    tmp = tmp * tmp
    tmp %= mod;
    p = p >> 1;
  return res


for i in xrange(M + 5):
  fact[i + 1] = (i + 1) * fact[i]
  fact[i + 1] %= mod;

if S + (n - 1) > M:
  print "NA"
else:
  a = fact[M - S + 1]
  b = fact[n]
  c = fact[M - S + 1 - n]

  ans = a * powmod((b * c) % mod, mod - 2)
  ans %= mod

  print ans