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.util.*;
import java.io.*;
import java.lang.*;
import java.math.BigInteger;
import java.nio.charset.StandardCharsets;

public class Main {
public static void main(String[] args) throws IOException{
  BufferedInputStream bis = new BufferedInputStream(System.in);
  BufferedReader r = new BufferedReader(new InputStreamReader(bis, StandardCharsets.UTF_8));
  PrintStream ps = new PrintStream(System.out);
  String str[]=r.readLine().trim().split(" ");
  BigInteger a = new BigInteger(str[0]);
  BigInteger b = new BigInteger(str[1]);
  BigInteger c = new BigInteger(str[2]);
  BigInteger d = new BigInteger(str[3]);

  BigInteger amax;
  BigInteger bmax;
  BigInteger result;

  if (a.multiply(c).compareTo(a.multiply(d)) > 1)
    amax = a.multiply(c);

  else
    amax = a.multiply(d);

  if (b.multiply(c).compareTo(b.multiply(d)) > 1)
    bmax = b.multiply(c);

  else
    bmax = b.multiply(d);

  if (amax.compareTo(bmax) > 1) 
    result = amax;
   else
    result = bmax;

  System.out.println(result);
  

  
}
}