Problem:
Score : 200 points

Problem Statement

Alice and Bob are controlling a robot. They each have one switch that controls the robot.

Alice started holding down her button A second after the start-up of the robot, and released her button B second after the start-up.

Bob started holding down his button C second after the start-up, and released his button D second after the start-up.

For how many seconds both Alice and Bob were holding down their buttons?

Constraints

0≤A<B≤100

0≤C<D≤100

All input values are integers.

Input

Input is given from Standard Input in the following format:

A B C D

Output

Print the length of the duration (in seconds) in which both Alice and Bob were holding down their buttons.

Sample Input 1

0 75 25 100

Sample Output 1

50

Alice started holding down her button 0 second after the start-up of the robot, and released her button 75 second after the start-up.

Bob started holding down his button 25 second after the start-up, and released his button 100 second after the start-up.

Therefore, the time when both of them were holding down their buttons, is the 50 seconds from 25 seconds after the start-up to 75 seconds after the start-up.

Sample Input 2

0 33 66 99

Sample Output 2

0

Alice and Bob were not holding their buttons at the same time, so the answer is zero seconds.

Sample Input 3

10 90 20 80

Sample Output 3

60

Solution in Go (1.6) (judge verdict: Wrong Answer)

package main

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

var sc = bufio.NewScanner(os.Stdin)

func nextInt() int {
	sc.Scan()
	i, e := strconv.Atoi(sc.Text())
	if e != nil {
		panic(e)
	}
	return i
}

func nextLine() string {
	sc.Scan()
	return sc.Text()
}

var grid [][]string

type alice struct {
	A int
	B int
}

type bob struct {
	C int
	D int
}

func main() {
	sc.Split(bufio.ScanWords)

	alice := alice{nextInt(), nextInt()}
	bob := bob{nextInt(), nextInt()}

	dt := 0

	if alice.A < bob.C && bob.C < alice.B {
		dt = alice.B - bob.C
	}

	if alice.A < bob.D && bob.D < alice.B {
		dt = alice.B - bob.D
	}

	if alice.A <= bob.C && alice.A <= bob.D && bob.C <= alice.B && bob.D <= alice.B {
		dt = bob.D - bob.C
	}

	if bob.C <= alice.A && bob.C <= alice.B && alice.A <= bob.D && alice.B <= bob.D {
		dt = alice.B - alice.A
	}

	fmt.Println(dt)

}