#include<bits/stdc++.h>
using namespace std;
int main(){
  int a,b,c,d;
  cin >> a>>b>>c>>d;
  if(b<=c || d<=a){
    cout << 0;
  }else{
    cout << min(b,d)-max(a,c);
  }
}
### Prompt

Construct a Cpp code solution to the problem outlined:

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.

Examples

Input

0 75 25 100


Output

50


Input

0 33 66 99


Output

0


Input

10 90 20 80


Output

60

### Response

```cpp
#include<bits/stdc++.h>
using namespace std;
int main(){
  int a,b,c,d;
  cin >> a>>b>>c>>d;
  if(b<=c || d<=a){
    cout << 0;
  }else{
    cout << min(b,d)-max(a,c);
  }
}
```