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 JavaScript (node.js v5.12) (judge verdict: Accepted)

'use strict';
let execute = input => {
  const TIME = input.split(' ').map(el => +el);
  let executing = [];
  for (let i = Number(TIME[0]); i < TIME[1]; i++) {
    executing[i] = executing[i] === undefined ? 1 : executing[i] + 1;
  }
  for (let i = Number(TIME[2]); i < TIME[3]; i++) {
    executing[i] = executing[i] === undefined ? 1 : executing[i] + 1;
  }
  let ans = executing.reduce((prev, cur) => {
    return cur === 2 ? prev + 1 : prev;
  }, 0);
  return ans;
};

function Main(input) {
  console.log(execute(input));
}
Main(require('fs').readFileSync('/dev/stdin', 'utf8'));