import java.util.Scanner;

public class Yukicoder48 {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int X = sc.nextInt();
		int Y = sc.nextInt();
		double L = sc.nextInt();
		int count = 0;
		
		if (Y < 0) count = 2;
		else if (X != 0) count = 1;
		
		count += Math.ceil(Math.abs(X) / L);
		count += Math.ceil(Math.abs(Y) / L);
		
		System.out.println(count);
	}
}