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 <iostream>
#include <vector>

using namespace std;

int main() {
	vector<int> a(4);
	int ma=0, mi = 0;

	for(int i=0;i<4;i++){
		cin >> a.at(i);
	}


	for (int i = 0; i < 2;i++) {
		int seki1 = 0,seki2 = 0;
		seki1 = a.at(i)* a.at(2);
		seki2 = a.at(i) * a.at(3);
		ma = max(ma,max(seki1,seki2));
	}

	cout << ma << endl;

}