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 1.8.0) (judge verdict: Accepted)

import java.util.Scanner;

public class Main {

  public static void main(String[] args) {
    int num[] = new int[4];
    Scanner scanner = new Scanner(System.in);
    for (int i = 0; i < 4; i++) {
      num[i] = Integer.parseInt(scanner.next());
    }
    scanner.close();
    long max = (long) num[0] * (long) num[2];
    long tmp = 0;

    if (num[0] > 0 && num[2] > 0) {
      max = (long) num[1] * (long) num[3];
    } else if (num[1] < 0 && num[3] < 0) {
      max = (long) num[0] * (long) num[2];
    } else {
      for (int j = 0; j < 2; j++) {
        for (int k = 2; k < 4; k++) {
          tmp = (long) num[j] * (long) num[k];
          if (max < tmp) {
            max = tmp;
          }
        }
      }
    }
    System.out.println(max);
  }
}