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>
#define ll long long int
int main(){
    ll a,b,c,d;
    scanf("%lld %lld %lld %lld",&a,&b,&c,&d);
    ll ans_a1 = a*c;
    ll ans_a2 = a*d;
    ll ans_b1 = b*c;
    ll ans_b2 = b*d;

    if (ans_a1>ans_a2&&ans_a1>ans_b1&&ans_a1>ans_b2){
        printf("%lld\n",ans_a1);
    }
    else if(ans_a2>ans_a1&&ans_a2>ans_b1&&ans_a2>ans_b2){
        printf("%lld\n",ans_a2);
    }
    else if(ans_b1>ans_a1&&ans_b1>ans_a2&&ans_b1>ans_b2){
        printf("%lld\n",ans_b1);
    }
    else{
        printf("%lld\n",ans_b2);
    }
    return 0;
}