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)

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        long[] params = new long[4];
        for (int i = 0; i < 4; i++) {
            params[i] = scanner.nextInt();
        }
        long a = params[0];
        long b = params[1];
        long c = params[2];
        long d = params[3];

        if (a >= 0) {
            if (c >= 0) {
                System.out.println(b * d);
            } else if (d >= 0) {
                System.out.println(b * d);
            } else {
                System.out.println(a * d);
            }
        } else if (b >= 0) {

            if (c >= 0) {
                System.out.println(b * d);
            } else if (d >= 0) {
                // a<0  b>=0   c<0  d>=0
                if (a * c  > b * d) {
                    System.out.println(a * c);
                } else {
                    System.out.println(b * d);
                }
            } else {
                System.out.println(a * c);
            }

        } else {

            if (c >= 0) {
                System.out.println(b * c);
            } else if (d >= 0) {
                System.out.println(a * c);
            } else {
                System.out.println(a * c);
            }

        }
    }
}