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;

class ABC070A
{
	static public void Main(string[] args)
	{
		int A,B,C,D;

		string[] vals = Console.ReadLine().Split(' ');
		A = int.Parse(vals[0]);
		B = int.Parse(vals[1]);
		C = int.Parse(vals[2]);
		D = int.Parse(vals[3]);
		

		if(D < A || B < C )
		{
			Console.WriteLine(0);
		}
		else
		{
			int s, e;

			if(A <= C)
			{
				s = C;
			}
			else
			{
				s = A;
			}

			if(B <= D)
			{
				e = B;
			}
			else
			{
				e = D;
			}
			Console.WriteLine(e - s);
		}
		

	}
}