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: Wrong Answer)

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

int maximum(int a, int b);

int main(){
	int a, b, c, d;
    int p1,p2,p3,p4;
    int sp1,sp2;
    int p;
	scanf("%d %d %d %d", &a,&b,&c,&d);

    p1 = a*c;
    p2 = a*d;
    p3 = b*c;
    p4 = b*d;

    sp1=maximum(p1,p2);
    sp2=maximum(p3,p4);
    p=maximum(sp1,sp2);

    printf("%d\n",p);

	return 0;
}

int maximum(int a, int b){
    if(a>b) return a ;
    else return b;
}