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>
#include <math.h>

int main(void) {
	signed int a;
	signed int b;
	signed int c;
	signed int d;
	signed long long ac;
	signed long long ad;
	signed long long bc;
	signed long long bd;
	signed long long output;

	scanf("%d %d %d %d", &a, &b , &c, &d);
	ac = (signed long long)a * c;
	ad = (signed long long)a * d;
	bc = (signed long long)b * c;
	bd = (signed long long)b * d;

	output = (signed long long)fmaxl((long double)ac, (long double)ad);
	output = (signed long long)fmaxl((long double)output , (long double)bc);
	output = (signed long long)fmaxl((long double)output, (long double)bd);

	printf("%d",output);

	return 0;
}