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 ans: int
	switch(R / M - L / M)
	case 0
		do ans :: R - L + 1
	case 1
		do ans :: M - L % M + R % M + 1
	default
		do ans :: M
	end switch
	do cui@print("\{ans}\n")
end func