import java.util.Scanner;
 
class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int x = sc.nextInt();
		int y = sc.nextInt();
		int l = sc.nextInt();
		int cnt = 0;
		if(y<0){
			cnt = 2;
		} else if(x != 0) {
			cnt = 1;
		}
		cnt += (Math.ceil(Math.abs(x)*1.0/l));
		cnt += (Math.ceil(Math.abs(y)*1.0/l));
		System.out.println(cnt);
	}
}