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 t1, t2, t3, t4;
    
    t1 = a * c;
    t2 = a * d;
    t3 = b * c;
    t4 = b * d;
    
    if (t1 > t2 && t1 > t3 && t1 > t4)
        printf("%lld", t1);
    if (t2 > t1 && t2 > t3 && t2 > t4)
        printf("%lld", t2);
    if (t3 > t1 && t3 > t2 && t3 > t4)
        printf("%lld", t3);
    if (t4 > t1 && t4 > t2 && t4 > t3)
        printf("%lld", t4);
   
    return 0;
}