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 Go (1.14.1) (judge verdict: Accepted)

package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
)

func StrStdin() string {
	scanner := bufio.NewScanner(os.Stdin)
	scanner.Scan()
	return strings.TrimSpace(scanner.Text())
}

func SliceStrsStdin(delim string) []string {
	stringInput := StrStdin()
	return SplitWithoutEmpty(stringInput, delim)
}

func SplitWithoutEmpty(stringTargeted string, delim string) []string {
	stringSplited := strings.Split(stringTargeted, delim)
	strs := []string{}

	for _, str := range stringSplited {
		if str != "" {
			strs = append(strs, str)
		}
	}
	return strs
}

func SliceIntStdin() []int {
	stringSplited := SliceStrsStdin(" ")

	intSlice := []int{}

	for ni := range stringSplited {
		num, _ := strconv.Atoi(stringSplited[ni])
		intSlice = append(intSlice, num)
	}

	return intSlice
}

func max(nums ...int) int {
	m := nums[0]
	for i, v := range nums {
		if i == 0 {
			continue
		}
		if m < v {
			m = v
		}
	}
	return m
}

func main() {

	abcd := SliceIntStdin()
	fmt.Println(max(abcd[0]*abcd[2], abcd[0]*abcd[3], abcd[1]*abcd[2], abcd[1]*abcd[3]))

}