# -*- coding:utf-8 -*-
if __name__ == "__main__":
	x,y = map(int,raw_input().split())
	x2,y2 = map(int,raw_input().split())
	ans = max(x,y)
	if min(x,0) <= x2 and x2 < max(x,0):
		if min(y,0) <= y2 and y2 < max(y,0):
			ans += 1
	print ans