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 long int a[4];
    long long int ans = (long long int)-1000000000000000003;
    int i, ii;
    scanf("%lld%lld%lld%lld", a, &a[1], &a[2], &a[3]);
    for (i = 0; i < 2; i++)
        for (ii = 2; ii < 4; ii++)
            if (ans < a[i] * a[ii])
                ans = a[i] * a[ii];
    printf("%lld", ans);
}