Problem Statement

Given are integers $a$, $b$, $c$, and $d$. We will choose integers $x$ and $y$ such that $a ≤ x ≤ b$ and $c ≤ y ≤ d$. Find the maximum possible value of $x - y$ here.

Constraints

• All values in input are integers.
• $-100 ≤ a ≤ b ≤ 100$
• $-100 ≤ c ≤ d ≤ 100$

Input

Input is given from Standard Input in the following format:

a b
c d

Output

Print the answer.