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 <stdlib.h>

int main (void) {
    long int a, b, c, d, e, f, g, h;
    scanf("%ld %ld %ld %ld", &a, &b, &c, &d);
    e = a * c;
    f = a * d;
    g = b * c;
    h = b * d;
    if (e > f && e > g && e > h) printf("%ld\n", e);
    else if (f > g && f > h) printf("%ld\n", f);
    else if (g > h) printf("%ld\n", g);
    else printf("%ld\n", h);
    return 0;
}