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: Wrong Answer)

import java.math.BigDecimal;
import java.util.Scanner;
public class Main {

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int a = in.nextInt();
		BigDecimal A = BigDecimal.valueOf(a);
		int b = in.nextInt();
		BigDecimal B = BigDecimal.valueOf(b);
		int c = in.nextInt();
		BigDecimal C = BigDecimal.valueOf(c);
		int d = in.nextInt();
		BigDecimal D = BigDecimal.valueOf(d);
		
		if(Math.signum(b) == 1.0 && Math.signum(d) == 1.0) {
			System.out.println(B.multiply(D));
		}else if(Math.signum(a) == -1.0 && Math.signum(c) == -1.0) {
			System.out.println(A.multiply(C));
		}else {
			BigDecimal AD = A.multiply(D);
			BigDecimal BC = B.multiply(C);
			if(AD.compareTo(BC) > 0) {
				System.out.println(AD);
			}else {
				System.out.println(BC);
			}
		}
	}
}