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.