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.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Arrays;

public class Main {

  public static void main(String[] args) throws Exception {
    try (final var stdin = new InputStreamReader(System.in);
         final var br = new BufferedReader(stdin)) {
      final var a = Arrays.stream(br.readLine().split(" "))
        .mapToLong(Long::parseLong)
        .toArray();

      System.out.println(
        Math.max(Math.max(Math.max(a[0] * a[2], a[1] * a[2]), a[0] * a[3]), a[1] * a[3])
      );
    }
  }
}