main = do
	x<- fmap read getLine
	y<- fmap read getLine
	l<- fmap read getLine
	let x_move=ceiling$abs$x/l
	let y_move=ceiling$abs$y/l
	let change_num=(if x/=0 then 1 else 0)+(if y<0 then 1 else 0)
	putStrLn$show$x_move+y_move+change_num