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>

int main()
{
	long a, b, c, d;
	long ac, ad, bc, bd;
	long max;

	scanf("%ld%ld%ld%ld", &a, &b, &c, &d);//提出時は scanf_s→scanf
	
	ac = a * c;
	ad = a * d;
	bc = b * c;
	bd = b * d;
	max = ac;

	if (max < ad) {
		max = ad;
	}
	if (max < bc) {
		max = bc;
	}
	if (max < bd) {
		max = bd;
	}

	printf("%ld",max);

	return 0;
}