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 C (GCC 9.2.1) (judge verdict: Accepted)

#include <stdio.h>
int main(void)
{
    long int a,b,c,d;
    scanf("%ld %ld %ld %ld", &a, &b, &c, &d);
    long int ac = a * c;
    long int ad = a * d;
    long int bc = b * c;
    long int bd = b * d;
    if (ac > ad)
    // ad
    {
        if (ac > bc)
        // ad bc
        {
            if (ac > bd)
            // ad bc bd
            {
                printf("%ld", ac);
            }
            else
            // ad bc ac
            {
                printf("%ld" ,bd);
            }
        }
        else
        // ad ac
        {
            if (bc > bd)
            // ad ac bd
            {
                printf("%ld", bc);
            }
            else
            // ad ac bc
            {
                printf("%ld", bd);
            }
        }
    }
    else
    // ac
    {
        if (ad > bc)
        // ac bc
        {
            if (ad > bd)
            // ac bc bd
            {
                printf("%ld", ad);
            }
            else
            // ac bc ad
            {
                printf("%ld", bd);
            }
        }
        else
        // ac ad
        {
            if (bc > bd)
            // ac ad bd
            {
                printf("%ld", bc);
            }
            else
            // ac ad bc
            {
                printf("%ld", bd);
            }
        }
    }
    return 0;
}