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;

namespace ABC070_B
{
    class Program
    {
        static string Solve()
        {
            string input = Console.ReadLine();
            int secA = int.Parse(input.Split(' ')[0]);
            int secB = int.Parse(input.Split(' ')[1]);
            int secC = int.Parse(input.Split(' ')[2]);
            int secD = int.Parse(input.Split(' ')[3]);
            if (secB > secC)
            {
                if (secD < secB)
                {
                    int countB = secD - secC;
                    return countB.ToString();
                }
                int countA = secB - secC;
                return countA.ToString();
            }
            return "0";
        }
        static void Main(string[] args)
        {
            Console.WriteLine(Solve());
        }
    }
}