import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);

        int x1 = in.nextInt();
        int y1 = in.nextInt();
        int x2 = in.nextInt();
        int y2 = in.nextInt();

        double dst1 = Math.sqrt(x1 * x1 + y1 * y1);
        double dst2 = Math.sqrt(x2 * x2 + y2 * y2);

        if (x1 * x2 < 0 || y1 * y2 < 0) {
            System.out.println((int)(Math.floor(dst1) + Math.floor(dst2)));
        }
        else {
            System.out.println((int)(Math.floor(Math.max(dst1, dst2)) - Math.ceil(Math.min(dst1, dst2)) + 1));
        }

    }
}