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( )
{
    long long int a , b , c , d ;
    scanf("%lld%lld%lld%lld" , &a , &b , &c , &d) ;
    
    long long int num[100] , i=0 , j , max;
    
    num[i] = a*c ;
    i++ ;
    max = num[0] ;
    
    num[i] = a*d ;
    i++ ;
    num[i] = b*c ;
    i++ ;
    num[i] = b*d ;
    
    j = ++i ;
    
    for( i = 0 ; i < j ; i++)
    {
        if( max < num[i])
            max = num[i] ;
    }
    
    printf("%lld\n" , max);
    
    return 0 ;
}