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++14 (GCC 5.4.1) (judge verdict: Accepted)

#include<iostream>
#include<algorithm>

using namespace std;

// Problem https://atcoder.jp/contests/abc070/tasks/abc070_b

int solver(int ASTART,int ASTOP,int BSTART,int BSTOP){
    int result;
    result = 0;
    int switchingtime;
    switchingtime = min(ASTOP,BSTOP)-max(ASTART,BSTART);
    if(0 < switchingtime){
        result = switchingtime;
    }
    return result;
}

int main(void){
    int A,B,C,D;
    int answer;
    answer = 0;
    cin >> A >> B >> C >> D;
    answer = solver(A,B,C,D);
    cout << answer;
    return 0;
}