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.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Reflection;

namespace CSharpConsoleApp {

    public class Program {
        public static int Main() {
            var input = Console.ReadLine().Split(' ').Select(s => int.Parse(s)).ToList();
            var A = input[0];
            var B = input[1];
            var C = input[2];
            var D = input[3];
            double result = 0;
            if (B <= C)
                result = 0;

            else if (A <= C && D <= B)
                result = D - C;
            else if (C <= A && B <= D)
                result = B - A;

            else if (A <= C && C <= B)
                result = B - C;
            else if (A <= D && D <= B)
                result = D - A;
            result.QBox();
            return 0;
        }
    }
}

public static class Extensions {
    public static void QBox<T>(this T t) {
        Console.WriteLine(t);
    }
}