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;

namespace atcoder_070B
{
    class MainClass
    {
        public static void Main(string[] args)
        {
			string[] array = Console.ReadLine().Split(' ');
			int A = int.Parse(array[0]);
			int B = int.Parse(array[1]);
			int C = int.Parse(array[2]);
			int D = int.Parse(array[3]);

			if (A - C >= 0 && D - B >= 0) 
			{
				Console.WriteLine(B - A);
				return;
			}
			
			if (C - A >= 0 && B - D >= 0) 
			{
				Console.WriteLine(D - C);
				return;
			}

			if (A - C >= 0 && D - A >= 0 && B - D >= 0) 
			{
				Console.WriteLine(D - A);
				return;
			}

			if (C - A >= 0 && B - C >= 0 && D - B >= 0) 
			{
				Console.WriteLine(B - C);
				return;
			}

			if (C - B >= 0 || A - D >= 0)
			{
				Console.WriteLine(0);
				return;
			}
        }
    }
}