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 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <stdio.h>
 
int main()
{
 
  /* 数値（整数） */
int a, b, c, d;


printf("");
scanf("%d %d %d %d", &a, &b, &c, &d);
    
if(0<=a&&a<b&&b<=100&&0<=c&&c<d&&d<=100)
{
    if(c<b)
    {
        printf("%d", b-c);
      
    }
    else if(a<d)
    {
        printf("%d", d-a);
    }
    else if(a<c&&d<b)
    {
        printf("%d", d-a);
    }
    else if(c<a&&b<d)
    {
        printf("%d", d-a);
    }
    else if(b<c||d<a)
    {
        printf("0");
    }
    
    
}
else
{
    printf("error");
}
    
 
    
    
  return 0;
}