import java.util.Scanner;

public class A000048 {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int x = sc.nextInt();
		int y = sc.nextInt();
		int l = sc.nextInt();
		sc.close();
		int r = 0;
		if(y<0)r++;
		if(x!=0) {
			r++;
			r+=((x>0?x:-x)-1)/l+1;
		}else if(y<0) {
			r++;
		}
		if(y!=0) {
			r+=((y>0?y:-y)-1)/l+1;
		}
		System.out.println(r);
	}
}