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: Wrong Answer)

"use strict";    
const main = arg => {
  	const Nums = arg.split("\n")[0].split(" ");
	const AliceMin = Nums[0]*1;
  	const AliceMax = Nums[1]*1;
   	const BobMin = Nums[2]*1;
   	const BobMax = Nums[3]*1;
  	let ans = 0;
  	// 部分的に被っているパターン
	if((AliceMax > BobMin) && (BobMax > AliceMax)){
    	ans = AliceMax - BobMin;
    } else if((AliceMax > BobMin) && (BobMax > AliceMax)){
    	ans = BobMax - BobMin;
    } else if((AliceMin < BobMin) && (BobMax < AliceMax)) {
      	ans = BobMax - BobMin;
    }
  
  	console.log(ans);
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));