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 static System.Console;
using static System.Math;
using System.Collections.Generic;
using System.Linq;

class Program
{
    public static void Main()
    {
        string[] inputSplit = ReadLine().Split(' ');

        int A = int.Parse(inputSplit[0]);
        int B = int.Parse(inputSplit[1]);
        int C = int.Parse(inputSplit[2]);
        int D = int.Parse(inputSplit[3]);
        int downTimeBothSwitch = 0;
        int upTimeBothSwitch = 0;
        int result = 0;

        if (B - C <= 0 || D - A <= 0) WriteLine("0");
        else
        {
            if (A < C) downTimeBothSwitch = C;
            else downTimeBothSwitch = A;
            if (B <= D) upTimeBothSwitch = B;
            else upTimeBothSwitch = D;
            WriteLine(upTimeBothSwitch - downTimeBothSwitch);
        }
    }
}