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>
#include <limits.h>

int main(int argc, char const *argv[])
{
    long long int a[4];

    scanf("%lld %lld %lld %lld", &a[0], &a[1], &a[2], &a[3]);

    long long int val[4];

    size_t k = 0;
    for (size_t i = 0; i < 2; i++)
    {
        for (size_t j = 2; j < 4; j++)
        {
            val[k++] = a[i] * a[j];
        }
    }

    long long int max = LLONG_MIN;
    for (size_t i = 0; i < 4; i++)
    {
        if (max < val[i])
        {
            max = val[i];
        }
    }

    printf("%lld\n", max);

    return 0;
}