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)

/*
 * Created by SharpDevelop.
 * User: Administrator
 * Date: 12/08/2017
 * Time: 21:24
 * 
 * To change this template use Tools | Options | Coding | Edit Standard Headers.
 */
using System;

namespace Two_Switches_AtCoder
{
	class Program
	{
		public static void Main(string[] args)
		{
			String[] s = Console.ReadLine().Split(' ');
			int a = int.Parse(s[0]);
			int b = int.Parse(s[1]);
			int c = int.Parse(s[2]);
			int d = int.Parse(s[3]);
			
			if (c>=b || a>=d) Console.WriteLine(0);
			else{
				if (c>=a && c<=b && d>b) Console.WriteLine(b-c);
				else{
					if (a>=c && a<=d && b>d) Console.WriteLine(d-a);
					else{
						if (a<=c && d<=b) Console.WriteLine(d-c);
						else if (c<=a && b<=d) Console.WriteLine(b-a);
					}
				}
			}
		}
	}
}