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 <string.h>
#define ll long long int


int main (){
	ll num[4]={0};
	scanf ("%lld %lld %lld %lld", &num[0], &num[1], &num[2], &num[3]);
	int sum = 0;
	for (int i=0; i<2; i++){
		for (int j=2; j<4; j++){
			if (sum < num[i]*num[j]){
				sum=num[i]*num[j];
			}
		}
	}
	printf ("%lld\n", sum);
	
	

return 0;
}