class Combi
  def initialize(max_n, mod = 10**9+7)
    @mod = mod
    @max_n = max_n
 
    @fac = Array.new(@max_n+1)
    @inv = Array.new(@max_n+1)
    @finv = Array.new(@max_n+1)
 
    @fac[0] = @fac[1] = 1
    @inv[1] = 1
    @finv[0] = @finv[1] = 1
    2.upto(@max_n) 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 nCk(n,k)
    @fac[n] * @finv[n - k] * @finv[k] % @mod
  end
end
 
x, y = gets.chomp.split.map(&:to_i)
 
x,y=y,x if x < y #=> y < x
 
if (x + y)%3!=0 || x/y > 2
  puts 0
  exit
end
 
layer = (x + y) / 3
num = x - layer
 
# p ['l', layer, num]
 
combi = Combi.new(10**6*3)
puts combi.nCk(layer, num)