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 1.8.0) (judge verdict: Wrong Answer)

import java.util.*;

public class Main {
    public static void main(String[] args) {
		Scanner sca01 = new Scanner(System.in);
		int a = sca01.nextInt();
		int b = sca01.nextInt();
		int c = sca01.nextInt();
		int d = sca01.nextInt();

		long maxAB = 0;
		long maxCD = 0;

		if(Math.signum(a) == -1.0 && Math.signum(c) == -1.0){
			maxAB = a;
		}else if(Math.signum(d) == -1.0){
			maxAB = a;
		}else if(a <= b){
			maxAB = b;
		}else {
			maxAB = a;
		}

		if(Math.signum(a) == -1.0 && Math.signum(c) == -1.0){
			maxCD = c;
		}else if(Math.signum(d) == -1.0){
			maxCD = d;
		}else if(c <= d){
			maxCD = d;
		}else {
			maxCD = c;
		}
		System.out.println(maxAB * maxCD);
	}
}