import java.util.Arrays;
import java.util.HashSet;
import java.util.Scanner;

class Main {
	public static void main(String[] args) throws Exception {
		new Main().run();
	}
	
	void run() {
		Scanner sc=new Scanner(System.in);
		long x=sc.nextLong();
		long y=sc.nextLong();
		long x1=sc.nextLong();
		long y1=sc.nextLong();
		long ans=Math.min(x, y)+Math.max(x, y)-Math.min(x, y);
		if(x==y&&x>x1&&y>y1&&x1==y1) {
			++ans;
		}
		System.out.println(ans);
	}
	
	static void tr(Object... objects) {
		System.out.println(Arrays.deepToString(objects));
	}
	
}