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 (Clang 10.0.0) (judge verdict: Wrong Answer)

//
//  main.c
//  No.2
//
//  Created by k18070kk on 2020/09/13.
//  Copyright © 2020 AIT. All rights reserved.
//

#include <stdio.h>

int main(int argc, const char * argv[]) {
    // insert code here...
    int a, b, c, d, ac, ad, bc, bd, m;
    scanf("%d %d %d %d", &a, &b, &c, &d);
    ac = a*c;
    printf("ac=%d\n", ac);
    ad = a*d;
    bc = b*c;
    bd = b*d;
    
    if(ac>=ad){
        m = ac;
    }else{
        m = ad;
    }
    printf("1:m=%d\n", m);
    if(bc>=m){
        m = bc;
    }
    printf("2:m=%d\n", m);
    if(bd>=m){
        m = bd;
    }
    printf("3:m=%d\n", m);
    printf("%d\n", m);
    
    return 0;
}