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 Rust (1.42.0) (judge verdict: Accepted)

use std::io;

fn procon_read<T: std::str::FromStr>() ->  Vec<T> {
    let mut buf = String::new();
    io::stdin().read_line(&mut buf).expect("");
    let iter = buf.split_whitespace();
    let mut v: Vec<T> = Vec::new();
    for i in iter {
        v.push(i.parse().ok().unwrap());
    }
    v
}

fn main() {
    let v:Vec<i128> = procon_read();
    let mut maxv:Vec<i128> = Vec::new();
    maxv.push(v[0]*v[2]);
    maxv.push(v[0]*v[3]);
    maxv.push(v[1]*v[2]);
    maxv.push(v[1]*v[3]);
    maxv.sort();
    println!("{}", maxv[3]);
}