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 <bits/stdc++.h>
#define x first
#define y second
#define mp make_pair
#define all(a) a.begin(), a.end()
#define pub push_back
#define ll long long
					  
using namespace std;



int main(){
	//freopen("input.txt", "r", stdin);
	//freopen("output.txt", "w", stdout);
	//freopen("seating.in", "r", stdin);
	//freopen("seating.out", "w", stdout);
	int l1, l2, r1, r2;
	cin >> l1 >> r1 >> l2 >> r2;
	l1 = max(l1, l2);
	r1 = min(r1, r2);
	cout << max(0, r1 - l1);	
}