func main()
	var ss: [][]char
	do ss :: cui@input().split(" ")
	var x: int :: ss[0].toInt(&)
	var y: int :: ss[1].toInt(&)
	do ss :: cui@input().split(" ")
	var x2: int :: ss[0].toInt(&)
	var y2: int :: ss[1].toInt(&)
	var ans: int :: [x.abs(), y.abs()].max()
	block b
		if(x.abs() <> y.abs())
			break b
		end if
		if(x2.abs() <> y2.abs())
			break b
		end if
		if(x.sign() <> x2.sign())
			break b
		end if
		if(y.sign() <> y2.sign())
			break b
		end if
		if(x.abs() < x2.abs())
			break b
		end if
		if(y.abs() < y2.abs())
			break b
		end if
		do ans :+ 1
	end block
	do cui@print("\{ans}\n")
end func