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>
long long int* bubbleSort(long long int* N, int len){
  int i,j;
  long long int temp;
  for(i=0; i<len; i++){
    for(j=len-1; j>i; j--){
      if(N[j] < N[j-1]){
        temp = N[j];
        N[j] = N[j-1];
        N[j-1] = temp;
      }
    }
  }

  return N;
}

int main(){
  long int a,b,c,d;
  scanf("%ld %ld %ld %ld", &a, &b, &c, &d);
long long int ans[4];
ans[0] = a*c;
ans[1] = a *d;
ans[2] = b *c;
ans[3] = b *d;
bubbleSort(ans, 4);
printf("%lld\n", ans[3]);
  return 0;
}