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: Runtime Error)

#include<stdio.h>

int abs(int a){
  if(a>=0){
  }else{
    a=-1*a;
  }
  return a;
}

int main(void){
  int N;
  scanf("%d",&N);
   
  long long x[N],y[N];
  for(int w=0;w<N;w++){
     scanf("%lld %lld",&x[w],&y[w]);
  }
  
  int i=0,j=i+1;
  int p=0,q;
  for(;i<N;i++){
    for(;j<N;j++){
      q=abs(x[i]-x[j])+abs(y[i]-y[j]);
      if(p<q)p=q;
    }
  }
  printf("%d",p);
}