class Fractional
    attr_reader :mod

    def initialize(max, mod)
        @max = max
        @mod = mod
        @frac     = { 0 => 1, 1 => 1 }
        @frac_inv = { 0 => 1, 1 => 1 }
        @inv      = {         1 => 1 }

        pre_calc(max)
    end

    def pre_calc(max)
        2.upto(max) do |i|
            @frac[i] = @frac[i - 1] * i % @mod;
            @inv[i] = @mod - @inv[@mod % i] * (@mod / i) % @mod
            @frac_inv[i] = @frac_inv[i - 1] * @inv[i] % @mod
        end
    end

    def at(i)
        @frac[i]
    end

    def inv_at(i)
        @frac_inv[i]
    end
end

class Combination
  def initialize(fraction)
      @fraction = fraction
  end

  def calc(n, r)
      return 0 if n < r
      return 0 if (n < 0 || r < 0)

      denom_inv = (@fraction.inv_at(r) * @fraction.inv_at(n - r) % @fraction.mod)
      return @fraction.at(n) * denom_inv % @fraction.mod
  end
end

x, y = gets.chomp!.split(" ").map(&:to_i)
min, max = [x, y].minmax

if min * 2 < max
  puts 0
  exit 0
end

if (x + y) % 3 != 0
  puts 0
  exit 0
end

frac = Fractional.new(10 ** 6 - 1, 10 ** 9 + 7)
comb = Combination.new(frac)

p = (x + y) / 3
r = 
  if p % 2 == 0
    p / 2 - (max - min) / 2
  else
    p / 2 - ((max - min) / 2)
  end

puts comb.calc(p, r)
