Score : $200$ points

Problem Statement

Given are integers $a,b,c$ and $d$. If $x$ and $y$ are integers and $a \leq x \leq b$ and $c\leq y \leq d$ hold, what is the maximum possible value of $x \times y$?

Constraints

• $-10^9 \leq a \leq b \leq 10^9$
• $-10^9 \leq c \leq d \leq 10^9$
• All values in input are integers.

Input

Input is given from Standard Input in the following format:

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

Output

Print the answer.

1 2 1 1

2

If $x = 1$ and $y = 1$ then $x \times y = 1$. If $x = 2$ and $y = 1$ then $x \times y = 2$. Therefore, the answer is $2$.

3 5 -4 -2

-6

The answer can be negative.

-1000000000 0 -1000000000 0

1000000000000000000