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 (Clang 10.0.0) (judge verdict: Accepted)

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

int main(void) {
	long long int a, b, c, d;
	int i, fin;
	long long int p[4], temp;
	char buf[128], *ch;

	fgets(buf, sizeof(buf), stdin);
	ch = strtok(buf, " ");
	a = atoi(ch);
	ch = strtok(NULL, " ");
	b = atoi(ch);
	ch = strtok(NULL, " ");
	c = atoi(ch);
	ch = strtok(NULL, " ");
	d = atoi(ch);

	p[0] = a * c;
	p[1] = a * d;
	p[2] = b * c;
	p[3] = b * d;

	fin = 0;
	while(fin < 3) {
		for(i = 0; i < 3; i += 1) {
			if(p[i] < p[i + 1]) {
				fin = 0;
				temp = p[i];
				p[i] = p[i + 1];
				p[i + 1] = temp;
			} else {
				fin += 1;
			}
		}
	}

	printf("%lld\n", p[0]);

	return 0;
}