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.

Examples

Input

1 2 1 1

Output

2

Input

3 5 -4 -2

Output

-6

Input

-1000000000 0 -1000000000 0

Output

1000000000000000000

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见题面