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 <iostream>
#include <vector>

using namespace std;

int main() {
	vector<long long int> a(4);
	long long int ans1=0,ans2=0;
	long long int seki1, seki2,seki3,seki4;

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



		seki1 = a.at(0)* a.at(2);
		seki2 = a.at(0) * a.at(3);
		ans1 = max(seki1,seki2);
		
		seki3 = a.at(1) * a.at(2);
		seki4 = a.at(1) * a.at(3);
		ans2 = max(seki3, seki4);


	cout << max(ans1,ans2) << endl;

}