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> 

int main() {
  int a, b, c, d;
  int ans1, ans2, ans;

  scanf("%d%d%d%d", &a, &b, &c, &d);

  int x1 = a * c;
  int x2 = a * d;
  int x3 = b * c;
  int x4 = b * d;

  if (x1 < x2) {
    ans1 = x2;
  } else {
    ans1 = x1;
  }

  if (x3 < x4) {
    ans2 = x4;
  } else {
    ans2 = x3;
  }

  if (ans1 < ans2) {
    ans = ans2;
  }  else {
    ans = ans1;
  }

  printf("%d", ans);

  return 0;
}