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;

/**
 * Created by enpingkuang on 2020/9/13 8:01 下午
 */
public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        long[] a = new long[4];
        long sum = Long.MIN_VALUE;
        for(int i = 0;i<4;i++){
            a[i] = scanner.nextLong();
        }
        sum = Math.max(sum,a[0]*a[2]);
        sum = Math.max(sum,a[0]*a[3]);
        sum = Math.max(sum,a[1]*a[2]);
        sum = Math.max(sum,a[1]*a[3]);
        System.out.println(sum);
    }
}