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 C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;

public class Hello{
    public static void Main(){
        string[] s=Console.ReadLine().Split();
        int a=int.Parse(s[0]);
        int a2=int.Parse(s[1]);
        int b=int.Parse(s[2]);
        int b2=int.Parse(s[3]);
        
        int kai,syu;
        
        if(a>b){
            kai=a;
        }else{
            kai=b;
        }
        
        if(a2>b2){
            syu=b2;
        }else{
            syu=a2;
        }
        
        Console.WriteLine(syu-kai);
        
    }
}