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>
#include<math.h>
#include<cstdio>
#include<ctype.h>
#include<stdio.h>
#include<set>
#include<vector>
#include<map>
#include<functional>
#include<iomanip>
#include<queue>
#include<ciso646>
#include<random>
#include<numeric>
#include<string>
typedef long long ll;
using namespace std;

ll gcd(ll a, ll b){
if(a<b){return gcd(b,a);}
else if(a%b){return gcd(b,a%b);}
else{return b;}
}
int main(){
  ll a,b,c,d;
  cin>>a>>b>>c>>d;
  if(max(a,c)-min(b,d)<0)
  cout<<min(b,d)-max(a,c)<<endl;
  else
  cout<<0<<endl;
  }