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: Accepted)

object Main extends App {
	val temp = scala.io.StdIn.readLine.split(" ").map(_.toInt)

	val A = temp(0)
	val B = temp(1)
	val C = temp(2)
	val D = temp(3)

	def max(x: Int, y: Int): Int = {
		if(x < y) return y
		else x
	}

	def min(x: Int, y: Int): Int = {
		if(x < y) return x
		else y
	}

	val re = min(B,D) - max(A,C)

	if(re<0) println(0)
	else println(re)
}