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>
#include<stdlib.h>
int main(){
    int flag=0;
    long long int a[4]={0},product[6]={0};
    scanf("%lld%lld%lld%lld",&a[0],&a[1],&a[2],&a[3]);
  for(int i=0;i<3;i++)
  product[i]=a[0]*a[i+1];
  for(int i=2;i<=3;i++)
  product[1+i]=a[1]*a[i];
  product[5]=a[2]*a[3];
  do{
        flag=0;
        for(int i=1;i<6;i++){
            long long int temp=0;
            if(product[i-1]<product[i]){
                temp=a[i-1];
                product[i-1]=product[i];
                product[i]=a[i-1];
                flag++;
            }
        }
    }while(flag);
  printf("%lld",product[0]);
}