import java.util.Scanner;

public class No48 {

    public static void main(String[] args) {
        Scanner s = new Scanner(System.in);
        int x = s.nextInt();
        int y = s.nextInt();
        int l = s.nextInt();

        int turn = 0;
        if (y < 0) {
            turn = 2;
        } else if (x != 0) {
            turn = 1;
        }

        x = Math.abs(x);
        y = Math.abs(y);

        int steps = ((x + l - 1) / l) + ((y + l - 1) / l) + turn;
        System.out.println(steps);
    }
}