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# (.NET Core 3.1.201) (judge verdict: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            long[] ABCD = Console.ReadLine().Split(' ').Select(i => long.Parse(i)).ToArray();
            //C <= A
            if (ABCD[2] <= ABCD[1])
            {
                //D <= B
                if (ABCD[3] <= ABCD[1])
                {
                    //D - C
                    Console.WriteLine(ABCD[3] - ABCD[2]);
                    return;
                }
                else if(ABCD[1] < ABCD[3])
                {
                    //B - A
                    Console.WriteLine(ABCD[1] - ABCD[0]);
                    return;
                }
                //B - C
                Console.WriteLine(ABCD[1] - ABCD[2]);
            }
            //C <= A
            else if(ABCD[2] <= ABCD[0])
            {
                //B <= D
                if(ABCD[1] <= ABCD[3])
                {
                    //B - A
                    Console.WriteLine(ABCD[1] - ABCD[0]);
                    return;
                }
                //D - A
                Console.WriteLine(ABCD[3] - ABCD[0]);

            }
            //B <= C || D <= A
            else if(ABCD[1] <= ABCD[2] || ABCD[3] <= ABCD[0])
            {
                Console.WriteLine(0);
            }
        }
    }
}
// 文字列の入力
//string s = Console.ReadLine();

// 整数の入力
//long n = long.Parse(Console.ReadLine());

// 文字列配列の入力
//string[] inputStrArray = Console.ReadLine().Split(' ');

// 整数配列の入力
//long[] inputLongArray = Console.ReadLine().Split(' ').Select(i => long.Parse(i)).ToArray();


//Console.WriteLine(ans);