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 Kotlin (1.3.71) (judge verdict: Accepted)

private fun readInt() = readLine()!!.toInt()

private fun readInts() = readLine()!!.split(' ').map { it.toLong() }

fun main() {
    val v = readInts()
    val a = v.take(2)
    val b = v.takeLast(2)
    val x = listOf(a[0]*b[0], a[0]*b[1], a[1]*b[0], a[1]*b[1])
    println(x.max()!!)
}