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: Accepted)

using System;
using System.Linq;
public class Hello{
    public static void Main()
    {
        // Your code here!
        int[] s = Console.ReadLine().Split(' ').Select(x => int.Parse(x)).ToArray();
        int A = s[0];
        int B = s[1];
        int C = s[2];
        int D = s[3];
        int ans = -1;
        if(D <= A || B <= C) ans = 0;
        else if((C <= A && A <= D) && D <= B) ans = D - A;
        else if(A <= C && D <= B) ans = D - C;
        else if((A <= C && C <= B) && B <= D) ans = B - C;
        else if(C <= A && B <= D) ans = B - A;
        
        Console.WriteLine(ans);
    }
}