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<iostream>

using namespace std;

int main(void){
	int a,b,c,d;
	int aa[101],bb[101],fg=0,saisyo,saigo;
	
	cin>>a;
	cin>>b;
	cin>>c;
	cin>>d;
	
	for(int lop=0;lop<100;lop++){
		if(a<=lop && lop<=b){
			aa[lop]=1;
		}else{
			aa[lop]=0;
		}
		if(c<=lop && lop<=d){
			bb[lop]=1;
		}else{
			bb[lop]=0;
		}
	}
	
	for(int lop=0;lop<100;lop++){
		if(aa[lop]==1 && bb[lop]==1 && fg==0){
			fg=1;
			saisyo=lop;
		}else if( (aa[lop]==0 || bb[lop]==0) && fg==1){
			saigo=lop-1;
			break;
		}
	}
	
	cout<<saigo-saisyo<<endl;
	
	return 0;
}