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: Wrong Answer)

#include<bits/stdc++.h>
using namespace std;
int digit(int,long long);
void ABC060(int,int,int);
void ABC058(string,string);
void line(int);
int main(){	
	int a[4];
	cin>>a[0]>>a[1]>>a[2]>>a[3];
	if(a[2]>a[1]){
		cout<<0<<endl;
		return 0;
	}
	sort(a,a+4);
	cout<<a[2]-a[1]<<endl;
}
void ABC060(int a,int b,int c){
	
	for(int u=1;u<100;u++){
		if(a*u%b==c){
			cout<<"YES"<<endl;
			break;
			}
		else if(a*u%b==0){
			cout<<"NO"<<endl;
			break;
		}
	}
}
int digit(int n,long long dig){
	return n%(dig*10)/dig;
}
void ABC058(string o,string e){
	int z=o.size(),x=e.size();
	for(int i=0;i<z+x;i++){
		if(i%2==0){
			cout<<o[i/2];
		}
		else{
			cout<<e[(i+1)/2-1];
		}
	}
	cout<<endl;
}
void line(int w){
	for(int k=0;k<w+2;k++){
		cout<<"#";
	}
	cout<<endl;
}