mod = 1000000007
n = gets.to_i
a = gets.split(" ").map &:to_i
if a[0] == 0
  p 1
  exit
end
n = n - a.sum + 1
m = a.length
if(n < m)
  puts "NA"
  exit
end
f = 1
def pm(a, b, c)
  ret = 1
  while b > 0
    ret = ret * a % c if b & 1 > 0
    a = a * a % c;
    b /= 2
  end
  ret
end
fn = fm = fnm = 1;
(1..n).each do |i|
  f = f * i % mod
  fn = f if i == n
  fm = pm(f, mod - 2, mod) if i == m
  fnm = pm(f, mod - 2, mod) if i == n - m
end
puts fnm * fn % mod * fm % mod