import java.io.BufferedReader;
import java.io.InputStreamReader;

public class No208 {
    public static void main(String[] args) {
        try {
            BufferedReader br = new BufferedReader(new InputStreamReader(
                    System.in));
            int[] a = strToIntArray(br.readLine());
            long x = a[0];
            long y = a[1];
            a = strToIntArray(br.readLine());
            long x2 = a[0];
            long y2 = a[1];
            long min = Math.min(x, y);
            long sub = Math.abs(x - y);

            boolean isSameSide = x * x2 > 0 && y * y2 > 0;

            if (Math.abs(x2) - Math.abs(y2) == 0 && isSameSide) {
                System.out.println(min + sub + 3);
            } else {
                System.out.println(min + sub);
            }
        } catch (Exception e) {
            System.err.println("Error:" + e.getMessage());
        }
    }

    static int[] strToIntArray(String S) {
        String[] strArray = S.split(" ");
        int[] intArray = new int[strArray.length];
        for (int i = 0; i < strArray.length; i++) {
            intArray[i] = Integer.parseInt(strArray[i]);
        }
        return intArray;
    }
}