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 Rust (1.15.1) (judge verdict: Accepted)

use std::io;

fn read_lines() -> Vec<i32> {
    let mut line = String::new();
    io::stdin().read_line(&mut line).unwrap();
    return line.split_whitespace().map(|x| x.trim().parse::<i32>().unwrap()).collect::<Vec<i32>>();
 }

 fn calcu_overlap(start_a: i32, end_a: i32, start_b: i32, end_b: i32) -> i32 {
     if end_a <= start_b  || start_a >= end_b{
         return 0;
     }
     let start = if start_a < start_b {
         start_b
     } else {
         start_a
     };

     let end = if end_a < end_b {
         end_a
     } else {
         end_b
     };
     return end - start
}

 fn main() {
     let input = read_lines();
     println!("{}", calcu_overlap(input[0], input[1], input[2], input[3]))
 }