    x,y = gets.chomp.split(" ").map(&:to_i)
    
    a = (2 * y) - x
    b = (2 * x) - y
    
    MOD = (10 ** 9) + 7
 
    
    if (a < 0) or (b < 0) or (a % 3 != 0) or (b % 3 != 0)
      puts 0
    else
        
      def kaijo(a, b)
        return (a..b).inject(1) {|i, j| (i * j) % MOD}
      end
   
      def joho_gyakugen(a, b)
        return ruijo(kaijo(a, b), MOD-2)
      end
      
      def ruijo(tei, bekisu)
        if bekisu == 0
          return 1
        elsif bekisu % 2 == 0
          return ruijo((tei ** 2) % MOD, bekisu / 2)
        else
          return tei * ruijo((tei ** 2) % MOD, bekisu / 2)
        end
      end
   
      n = [a, b].min / 3
      m = [a, b].max / 3
      total = n + m
      #if n == 0
        #puts 1
      #else
        result = (kaijo(m + 1, total) * joho_gyakugen(1, n))
        puts result % MOD
      #end
    end