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>
#include<cstdio>
#include<iomanip>
#include<algorithm>
#include<vector>
#include<set>
#include<list>
#include<queue>
#include<deque>
#include<unordered_map>
#include<map>
#include<string>
#include<cstring>
#include<stack>
#include<cmath>

#define vint vector<int>
#define vstr vector<string>
#define vll vector<long long>
#define ll long long
#define pf printf
#define sf scanf
#define sfd(n) scanf("%d", &n)
#define sflf(n) scanf("%lf", &n)
#define sfll(n) scanf("%lld", &n)
#define pfd(n) printf("%d", n)
#define pflf(n) printf("%lf", n)
#define pfll(n) printf("%lld", n)
#define pft	printf("\t")
#define pfn printf("\n")
#define pfk printf(" ")
#define PI 3.1415926
#define MAX 100000
#define M 100003

using namespace std;

int main() {
	int a, b, c, d, ans = 0;
	sfd(a);
	sfd(b);
	sfd(c);
	sfd(d);
	if( a<c ) {
		if( c<b ) {
			if( b>=d ) {
				ans = d-c;
			}else {
				ans = b-c;
			}
		}
	}else{
		if( b>a ) {
			if( b>=d ) {
				ans = d-a;
			}else {
				ans = b-a;
			}
		}
		
	}
	pfd(ans);
	
	return 0;
}