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 Scala (2.11.7) (judge verdict: Wrong Answer)

object Main {
    def main(args: Array[String]) : Unit = {
        val sc = new java.util.Scanner(System.in)
        val a, b, c, d  = sc.nextInt
        println(calc(a, b, c, d))
    }
    def calc(a: Int, b: Int, c: Int, d: Int) : Int = {
        var ans = max(b - c, 0)
        if (ans > 0 && b - d > 0) {
            ans -= b - d
        }
        ans
    }
    def max(a: Int, b: Int) : Int = { if (a > b) a else b }
}