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 (Clang 10.0.0) (judge verdict: Wrong Answer)


#include <stdio.h>

int main(){

    long long a, b, c, d;

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

    long long x[4];

    x[0] = a*c;
    x[1] = a*d;
    x[2] = b*c;
    x[3] = b*d;

    long long max = x[0];

    for(int i=0;i<4;i++){
        if(max<x[i]){
            max = x[i];
        }
    }

    printf("%lu\n", max);

    return 0;
}