func main()
	var _: [][]char :: cui@input().split(" ")
	var A: int :: _[0].toInt(&)
	var B: int :: _[1].toInt(&)
	var ans: int
	for i(A, B)
		if((A + B + i) % 3 = 0)
			do ans :+ 1
		end if
	end for
	do cui@print("\{ans}\n")
end func