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 (1.42.0) (judge verdict: Accepted)

#![allow(non_snake_case)]
use proconio::input;
use std::collections::HashMap;
// use std::cmp::max;
// use std::cmp::min;


fn main() {
    input! {
        A: i64,
        B: i64,
        C: i64,
        D: i64,
    }

    let mut is_on_map = vec![0i64; 1000];

    for i in A..B + 1 {
        is_on_map[i as usize] = 1;
    }

    let mut ans = 0;
    for i in C..D + 1 {
        if is_on_map[i as usize] == 1 {
            ans += 1;
        }
    }

    // 間隔を数えるので植木算
    if ans == 0 {
        ans = 0;
    } else {
        ans -= 1;
    }
    println!("{}", ans);
}