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.*;
/**
 * Created by 卢嘉昊 on 2017/8/12.
 */
public class Main {
    public static void main(String[] args){
        Scanner scan = new Scanner(System.in);
        int A = scan.nextInt();
        int B = scan.nextInt();
        int C = scan.nextInt();
        int D = scan.nextInt();
        int Alice = B-A;
        int Bob = D-C;
        int res = 0;
        if(A<C){
            if(B<C) res = 0;
            else if(B>D) res = Bob;
            else res = B-C;
        }else if(A == C){
            res = Alice < Bob ? Alice : Bob;
        }else{
            if(A>=D) res = 0;
            else if(B>D) res = D-A;
            else res = B-A;
        }
        System.out.println(res);
    }
}