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 <inttypes.h>

int main(){
    __int64_t a, b, c, d, z;
    
    scanf("%" PRId64, &a);
    scanf("%" PRId64, &b);
    scanf("%" PRId64, &c);
    scanf("%" PRId64, &d);
    
    z=a*c;
    if(z<a*d){
        z=a*d;
    }
    if(z<b*c){
        z=b*c;
    }
    if(z<b*d){
        z=b*d;
    }

    printf("%" PRId64 "\n", z);

    return 0;
}