import java.util.Scanner;

public class Ousho {

	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		int x = s.nextInt(),y = s.nextInt(),x2 = s.nextInt(),y2 = s.nextInt();
		s.close();
		int count = 0;
		if(x == y){
			if(x2 == y2 && x > x2){
				count = x+1;
			}else{
				count = x;
			}
		}else{
			count = Math.min(x, y) + Math.abs(x-y);
		}
		System.out.println(count);
	}

}