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>
#define rep(x, y) for(int x = 0; x < (y); x++)
#define REP(x, z, y) for(int x = (z); x < (y); x++)
#define all(x) x.begin(), x.end()
#define len(x) (sizeof(x) / sizeof(x[0]))
#define split_str(str, sp_word) istringstream stream(str); string res; for(int cnt = 0; getline(stream,res,sp_word); cnt++)
#define scanln(x) fgets(x, sizeof x, stdin)
#define down_queue(x) priority_queue<x>
#define up_queue(x) priority_queue<x, vector<x>, greater<x>>
#define i_str(x) atoi(x.c_str())
#define digit(x) ((int)log10((double)(x)) + 1)
#define mp(x,y) make_pair(x,y)
#define pb(x) push_back(x)
#define pf(x) push_front(x)
#define out(x) cout << (x) << endl;
#define outs(x) for(auto i : x) cout << i << " ";
using namespace std;
const int MOD = 1000000007; 
typedef long long ll;
typedef string str;

int main() {
  int a,b,c,d; cin >> a >> b >> c >> d;
  if(b <= c) puts("0");
  else cout << b - c - a;
  return 0;
}