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.io.FileNotFoundException;
import java.math.BigInteger;
import java.util.Arrays;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws FileNotFoundException {

		//    	File file = new File("src/in.txt");
		//    	Scanner sc = new Scanner(file);

		Scanner sc = new Scanner(System.in);

		int a = sc.nextInt();
		int b = sc.nextInt();
		int c = sc.nextInt();
		int d = sc.nextInt();


		BigInteger[] ans = new BigInteger[6];
		ans[0] = BigInteger.valueOf(a).multiply(BigInteger.valueOf(b));
		ans[1] = BigInteger.valueOf(a).multiply(BigInteger.valueOf(c));
		ans[2] = BigInteger.valueOf(a).multiply(BigInteger.valueOf(d));
		ans[3] = BigInteger.valueOf(b).multiply(BigInteger.valueOf(c));
		ans[4] = BigInteger.valueOf(b).multiply(BigInteger.valueOf(d));
		ans[5] = BigInteger.valueOf(c).multiply(BigInteger.valueOf(d));
		Arrays.sort(ans);
		System.out.println(ans[5]);

	}
}