class Combinator
  MAX = 2000000 # nCkの最大のnより大きいこと。MODより小さいこと。
  MOD = 1000000007

  def initialize
    @fac = Array.new(MAX)
    @fac[0] = 1
    @fac[1] = 1
    @finv = Array.new(MAX)
    @finv[0] = 1
    @finv[1] = 1
    @inv = Array.new(MAX)
    @inv[1] = 1
    (2..(MAX-1)).each do |i|
      @fac[i] = @fac[i-1]*i%MOD
      @inv[i] = MOD-@inv[MOD%i]*(MOD/i)%MOD
      @finv[i] = @finv[i-1]*@inv[i]%MOD
    end
  end

  def call(all, select)
    return 0 if all < select
    return 0 if all < 0||select < 0
    @fac[all]*(@finv[select]*@finv[all-select]%MOD)%MOD
  end
end
@combinator = Combinator.new

x, y = gets.split.map(&:to_i)
m = (2 * y - x) / 3
n = (2 * x - y) / 3
if m < 0 || n < 0 || x != m + 2 * n || y != n + 2 * m
  puts 0
  exit 0
end
puts @combinator.call(n+m, [n, m].min)

