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)

function Main(inp) {
    var input = inp.split('\n')[0].split(' ').map(function(n) {
        return Number(n);
    });
    var count = 0;
    for(var i = 0; i <= 100; i++) {
        var onA = false, onB = false;
        if (input[0] <= i && i < input[1]) {
            onA = true;
        }
        if (input[2] <= i && i < input[3]) {
            onB = true;
        }
        if (onA && onB) {
            count += 1;
        }
    }
    console.log(count);
}

Main(require("fs").readFileSync("/dev/stdin", "utf8"));