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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

class Main {
    public static void main(final String[] args) throws Exception {

        try (BufferedReader br = new BufferedReader(new InputStreamReader(System.in));) {
            List<String> inputNumbers = Arrays.asList(br.readLine().split(" "));
            int alicePressSecond = Integer.parseInt(inputNumbers.get(0));
            int aliceReleaseSecond = Integer.parseInt(inputNumbers.get(1));
            int bobPressSecond = Integer.parseInt(inputNumbers.get(2));
            int bobReleaseSecond = Integer.parseInt(inputNumbers.get(3));

            int maxPressSecond = bobPressSecond;
            if (alicePressSecond > bobPressSecond) {
                maxPressSecond = alicePressSecond;
            }
            
            int minReleaseSecond = bobReleaseSecond;
            if (aliceReleaseSecond < bobReleaseSecond) {
                minReleaseSecond = aliceReleaseSecond;
            }

            int ans = 0;
            if (maxPressSecond < minReleaseSecond) {
                ans = minReleaseSecond - maxPressSecond;
            }

            System.out.println(ans);
        } catch (IOException | NumberFormatException e) {
            e.printStackTrace();
            System.exit(0);
        } catch (final Exception e) {
            e.printStackTrace();
            System.exit(0);
        }
    }
}