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.util.ArrayList;
import java.util.Scanner;

public class Main {
    void run(String[] args){
        Scanner scan=new Scanner(System.in);
        Integer a=scan.nextInt();
        Integer b=scan.nextInt();
        Integer c=scan.nextInt();
        Integer d=scan.nextInt();
        Integer max=Integer.MIN_VALUE;
        Integer answer;
        ArrayList<Integer>x=new ArrayList<>();
        ArrayList<Integer>y=new ArrayList<>();
        x.add(a);
        x.add(b);
        y.add(c);
        y.add(d);
        for(Integer i=0;i<2;i++){
            for(Integer j=0;j<2;j++){
                answer=x.get(i)*y.get(j);
                if(max<=answer){
                    max=answer;
                }
            }
        }
        System.out.println(max);
    }
    public static void main(String args[]){
        Main printer = new Main();
        printer.run(args);
    }
}