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: Wrong Answer)

#include <stdio.h>

int main() {
    
    long long int a, b, c, d;
    scanf("%lld%lld%lld%lld", &a, &b, &c, &d);
    
    long long int t, x = a, y = c;
    
    if (a >= 0 && b >= 0 && c >= 0 && d >= 0 || a <= 0 && b <= 0 && c <= 0 && d <= 0 ) {
        
        if (a > b)
            x = a;
        else
            x = b;
        
        if (c > d)
            y = c;
        else
            y = d;
    
    } else if (a <= 0 && b <= 0) {
        if (a > b)
            x = a;
        else    
            x = b;
        
        if (c >= 0 && d >= 0)
            if (c > d)
                y = d;
            else
                y = c;
        
    } else if (c <= 0 && d <= 0) {
        if (c > d)
            y = c;
        else
            y = d;

        if (a >= 0 && b >= 0)
            if (a > b)
                x = b;
            else
                x = a;
    
    } 
    
    
    
    printf("%lld", x * y);
   
    return 0;
}