import java.util.Scanner;

public class Robo {

	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		int X = s.nextInt(), Y = s.nextInt(), L = s.nextInt(), count = 0;
		s.close();
		if(Y >= 0){
				count += COUNT(Y, L, count);
				count += COUNT(X,L,count) + 1;
		}else{
			if(X != 0){
				count += COUNT(X,L,count) + 1;
				count += COUNT(Y,L,count) + 1;
			}
			
		}
		System.out.println(count);

	}
	
	static int COUNT(int p,int k, int count){
		if(p%k == 0){
			count = Math.abs(p/k);
		}else{
			count = Math.abs(p/k) + 1;
		}
		return count;
	}

}