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: Wrong Answer)

public fun readln() = readLine()!!
public fun readlnByte() = readln().toByte()
public fun readlnShort() = readln().toShort()
public fun readlnInt() = readln().toInt()
public fun readlnLong() = readln().toLong()
public fun readlnFloat() = readln().toFloat()
public fun readlnDouble() = readln().toDouble()
public fun readlnBigInt(radix: Int = 10) = readln().toBigInteger(radix)
public fun readlnBigDecimal() = readln().toBigDecimal()

public fun lineSequence(limit: Int = Int.MAX_VALUE) = generateSequence { readLine() }.constrainOnce().take(limit)
public fun readlnStrings() = readln().split(' ')
public fun readlnBytes() = readlnStrings().map { it.toByte() }
public fun readlnShorts() = readlnStrings().map { it.toShort() }
public fun readlnInts() = readlnStrings().map { it.toInt() }
public fun readlnLongs() = readlnStrings().map { it.toLong() }
public fun readlnFloats() = readlnStrings().map { it.toFloat() }
public fun readlnDoubles() = readlnStrings().map { it.toDouble() }
fun main() {
    val (a, b, c, d) = readlnDoubles()
    val max = listOf(a*c, a*d, b*c, b*d).max()
    println(max)
}