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.math.BigInteger;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        long a = sc.nextLong();
        long b = sc.nextLong();
        long c = sc.nextLong();
        long d = sc.nextLong();

        BigInteger ac = BigInteger.valueOf(a).multiply(BigInteger.valueOf(c));
        BigInteger ad = BigInteger.valueOf(a).multiply(BigInteger.valueOf(d));

        BigInteger result1 = ac.max(ad);

        BigInteger bc = BigInteger.valueOf(b).multiply(BigInteger.valueOf(c));
        BigInteger bd = BigInteger.valueOf(b).multiply(BigInteger.valueOf(d));

        BigInteger result2 = bc.max(bd);

        System.out.println(result1.max(result2));

    }
}