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(void) {

	int a, b, c, d, max;
	int sum[4];

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

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

	max = sum[0];

	for (int i = 1; i < 4; i++) {
		if (max < sum[i]) {
			max = sum[i];
		}
	}

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

	return 0;
}