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<stdlib.h>
#include<string.h>
#include<math.h>

typedef long long int int64;
int64 max2(int64 a, int64 b) { return a > b ? a : b; }

int64 max3(int64 a, int64 b, int64 c) { return ((a > b ? a : b) > c ? (a > b ? a : b) : c); }

int main()
{
    int64 a,b,c,d;

    scanf("%lld %lld %lld %lld",&a,&b,&c,&d);

    printf("%lld",max2((a*c),max3((a*d),(b*c),(b*d))));
}