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.

Sample Input 1

0 10
0 10

Sample Output 1

10

$(x, y) = (10, 0)$ achieves the maximum value $x - y = 10$.

Sample Input 2

-100 -100
100 100

Sample Output 2

-200

Sample Input 3

-100 100
-100 100

Sample Output 3

200