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>

int main(void) {
	int a, b, c, d;
	scanf("%d%d%d%d", &a, &b, &c, &d);
	int ans1, ans2, ans3, ans4, seki;
	ans1 = a*c;
	ans2 = b*c;
	ans3 = a*d;
	ans4 = b*d;
	seki = ans1;
	if(seki < ans2){
		seki = ans2;
	}
	if(seki < ans3){
		seki = ans3;
	}
	if(seki < ans4){
		seki = ans4;
	}
	printf("%d", seki);
	return 0;
}