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: Runtime Error)

public class Main{
  public static void main(String[] args){
    int A = new java.util.Scanner(System.in).nextInt();
    int B = new java.util.Scanner(System.in).nextInt();
    int C = new java.util.Scanner(System.in).nextInt();
    int D = new java.util.Scanner(System.in).nextInt();

    int big;
    int small;
    int ans;

    //kagen
    if(A>=C){
      small = A;
    }
    else{
      small = C;
    }

    //jogen
    if(B>=D){
      big = D;
    }
    else{
      big = B;
    }

    ans = big-small;
    System.out.println(ans);
  }
}