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::*;
use std::io;
use std::str::FromStr;
use std::cmp;

fn read(s: &mut StdinLock) -> i32 {
    s.by_ref()
        .bytes()
        .map(|c| c.unwrap() as char)
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .fold(0, |a, x| (x as u8 - b'0') as i32 + a * 10)
}

fn main() {
    let stdin = io::stdin();
    let mut v = Vec::new();

    let mut s = stdin.lock();
    let s = &mut s;
    for _ in 0..4 {
        let n = read(s);
        v.push(n);
    }
    // println!("{}", cmp::min(v[1], v[3]));
    // println!("{}", cmp::max(v[0], v[2]));

    if cmp::min(v[1], v[3]) - cmp::max(v[0], v[2]) < 0 {
        println!("0");
        return;
    }

    println!("{}", cmp::min(v[1], v[3]) - cmp::max(v[0], v[2]));
}