func main()
	var ss: [][]char :: cui@input().split(" ")
	var L: int :: ss[0].toInt(&)
	var R: int :: ss[1].toInt(&)
	var M: int :: ss[2].toInt(&)
	var dic: dict<int, int> :: #dict<int, int>
	var ans: int
	for i(L, R)
		var n: int :: i % M
		if(!dic.exist(n))
			do dic.add(n, 1)
			do ans :+ 1
		end if
	end for
	do cui@print("\{ans}\n")
end func