import java.util.Scanner;

public class No048 {
	public static void main(String args[]){
		int x = 0;
		int y = 0;
		int distance = 0;
		int go = 0;
		int turn = 0;
		Scanner sc = new Scanner(System.in);

		x = sc.nextInt();
		y = sc.nextInt();
		go = sc.nextInt();

		//回頭に要する行為判定
		if(0<y && x==0){
			turn = 0;
		}else if(y==0 && x<0){
			turn = 1;
		}else if(0<y){
			turn = 1;

		}else if(y<0){
			turn = 2;
			y=y*-1;
			}


		if(y!=0){
			while(true){
				y=y-go;
				turn++;
				if(y<=0){
					break;
				}
			}
		}

		if(x<0){x=x*-1;}

		if(x!=0){
			while(true){
				x=x-go;
				turn++;
				if(x<=0){
					break;
				}
			}
		}


		System.out.println(turn);
	}
}