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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.*;
import static java.lang.Math.*;

public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);

		// 入力
		int a = sc.nextInt();// Alice A秒
		int b = sc.nextInt();// Alice B秒
		int c = sc.nextInt();// Bob C秒
		int d = sc.nextInt();// Bob D秒

		// 計算
		int t = 0;

		// abcd
		if(b <= c) t = 0;
		// acbd
		if(a <= c && c <= b && b <= d) t = b - c;
		// cabd
		if(c <= a && b <= d) t = b - a;
		// acdb
		if(a <= c && d <= b) t = d - c;
		// cadb
		if(c <= a && a <= d && d <= b) t = d - a;
		// cdab
		if(d <= a) t = 0;

		// 出力
		System.out.println(t);

	}
}