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Score : $100$ points

### 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:

$a$ $b$
$c$ $d$


### 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