import java.util.Arrays;
import java.util.LinkedList;
import java.util.Scanner;

public class Main {
	
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		final long x = sc.nextLong();
		final long y = sc.nextLong();
		final long x2 = sc.nextLong();
		final long y2 = sc.nextLong();
		
		final long opt = x + y - Math.min(x, y);
		
		if(x == y && x2 == y2 && x2 < x && y2 < y){
			System.out.println(opt + 1);
		}else if(x == 0 && x2 == 0 && y2 < y){
			System.out.println(opt);
		}else if(y == 0 && y2 == 0 && x2 < x){
			System.out.println(opt);
		}else {
			System.out.println(opt);
		}
	}
	
}