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<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<math.h>
#define true 1
#define false 0
#define MAX 1000000000
typedef long long ll;
typedef unsigned char Uchar; 

int main(void){

int i,j;
ll a,b,c,d;
  
scanf("%lld %lld %lld %lld",&a,&b,&c,&d);

//  printf("%lld,%lld,%lld,%lld",a,b,c,d);
  ll s[5];
  s[0] = a * c;
  s[1] = a * d;
  s[2] = b * c;
  s[3] = b * d;
  
  ll max = s[0];
  for(i=1;i<4;i++){
    if(max < s[i])	max = s[i];
//    printf("%lld,",s[i]);
  }
  
printf("%lld",max);

return 0;
}