lib C
  fun strtoll(s : UInt8*, p : UInt8**, b : Int32) : Int64
end

class String
  def to_i64
    C.strtoll(self, nil, 10)
  end
end

struct ModInt
  @@MOD = 1_000_000_007i64

  def self.mod
    @@MOD
  end

  def self.zero
    ModInt.new(0)
  end

  def initialize(n)
    @n = n.to_i64 % @@MOD
  end

  getter n : Int64

  def + : self
    self
  end

  def - : self
    ModInt.new(n != 0 ? @@MOD - @n : 0)
  end

  def +(m)
    ModInt.new(@n + m.to_i64 % @@MOD)
  end

  def -(m)
    ModInt.new(@n - m.to_i64 % @@MOD)
  end

  def *(m)
    ModInt.new(@n * m.to_i64 % @@MOD)
  end

  def /(m)
    raise DivisionByZeroError.new if m == 0
    a, b, u, v = m.to_i64, @@MOD, 1i64, 0i64
    while b != 0
      t = a // b
      a -= t * b
      a, b = b, a
      u -= t * v
      u, v = v, u
    end
    ModInt.new(@n * u)
  end

  def //(m)
    self / m
  end

  def **(m : Int)
    t, res = self, ModInt.new(1)
    while m > 0
      res *= t if m.odd?
      t *= t
      m >>= 1
    end
    res
  end

  def ==(m)
    @n == m.to_i64
  end

  def !=(m)
    @n != m.to_i64
  end

  def succ
    self + 1
  end

  def pred
    self - 1
  end

  def to_i64 : Int64
    @n
  end

  delegate to_s, to: @n
  delegate inspect, to: @n
end

struct Int
  def to_mint : ModInt
    ModInt.new(self)
  end
end

class Comb(T)
  def initialize(@Max = 3000009)
    @fac = Array(T).new(@Max, T.zero)
    @finv = Array(T).new(@Max, T.zero)
    @inv = Array(T).new(@Max, T.zero)
    @fac[0] = @fac[1] = T.new(1)
    @finv[0] = @finv[1] = T.new(1)
    @inv[1] = T.new(1)
    (2...@Max).each do |i|
      @fac[i] = @fac[i - 1] * i
      @inv[i] = -@inv[T.mod % i] * (T.mod / i)
      @finv[i] = @finv[i - 1] * @inv[i]
    end
  end

  def p(n, r)
    (n < r || n < 0 || r < 0) ? T.zero : @fac[n] * @finv[n - r]
  end

  def c(n, r)
    (n < r || n < 0 || r < 0) ? T.zero : @fac[n] * @finv[r] * @finv[n - r]
  end

  def h(n, r)
    (n < 0 || r < 0) ? T.zero : r == 0 ? T.new(1) : c(n + r - 1, r)
  end

  def fact(n)
    @fac[n]
  end
end

comb = Comb(ModInt).new

n = read_line.to_i
a = read_line.split.map(&.to_i)

if a.sum == 0
  puts 1
elsif (ans = comb.h(n - a.sum - a.size + 2, a.size)) != 0
  puts ans
else
  puts "NA"
end