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(/ /, <>);

if ($inputs[2] >= $inputs[1] || $inputs[0] >= $inputs[3]) {
    print("0");
} elsif ($inputs[0] <= $inputs[2] && $inputs[1] <= $inputs[3]) {
    print($inputs[1] - $inputs[2]);
} elsif ($inputs[2] <= $inputs[0] && $inputs[3] <= $inputs[1]) {
    print($inputs[3] - $inputs[0]);
} elsif ($inputs[0] <= $inputs[2] && $inputs[1] >= $inputs[3]) {
    print (($inputs[1] - $inputs[2]) - ($inputs[2] - $inputs[0]));
} elsif ($inputs[2] <= $inputs[0] && $inputs[3] >= $inputs[1]) {
    print (($inputs[3] - $inputs[0]) - ($inputs[0] - $inputs[2]));
} else {
    print("0");
}