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 Perl (v5.18.2) (judge verdict: Wrong Answer)

@inputs = split(/ /, <>);
$before1 = $inputs[0];
$before2 = $inputs[2];
$after1 = $inputs[1];
$after2 = $inputs[3];

if ($after2 >= $after1) {
    if ($after1 <= $before2) {
        print (0);
    } else {
        if ($before1 > $before2) {
            print ($after2 - $before2 - $before1);
        }else{
            print ($after1 - $before1 - $before2);
        }
    }
} elsif ($after2 < $after1) {
    if ($after2 <= $before1) {
        print (0);
    } else {
        if ($before2 > $before1) {
            print ($after1 - $before1 - $before2);
        }else {
            print ($after2 - $before2 - $before1);
        }
    }
}