Problem:
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.

Sample Input 1

1 2 1 1

Sample Output 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.

Sample Input 2

3 5 -4 -2

Sample Output 2

-6

The answer can be negative.

Sample Input 3

-1000000000 0 -1000000000 0

Sample Output 3

1000000000000000000

Solution in Java (OpenJDK 11.0.6) (judge verdict: Accepted)

public class Main {
	public static void main(String[] args) {
		var sc = new java.util.Scanner(System.in);
		var a = sc.nextBigInteger();
		var b = sc.nextBigInteger();
		var c=sc.nextBigInteger();
		var d = sc.nextBigInteger();
		var ac = a.multiply(c);
		var ad = a.multiply(d);
		var bd = b.multiply(d);
		var bc = b.multiply(c);
		System.out.println(ad.max(ac.max(bc.max(bd))));
	}
}