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(input) {
	var tmp = input.split(" ");
	var a = parseInt(tmp[0], 10);
	var b = parseInt(tmp[1], 10);
	var c = parseInt(tmp[2], 10);
	var d = parseInt(tmp[3], 10);
        if(b < c || d < a) {
            //   a   b   c  d
           console.log("%d", 0);
        } else if( a < c ) {
            if( b < d) { 
              //   a  c  b  d
              console.log("%d", b - c );
            }  else  {
             //  a  c  d   b 
              console.log("%d",  d - c);
           }
        } else {
           if( b < d) { 
              //  c a  b  d
              console.log("%d", b - a );
            }  else  {
             //  c a d  b 
              console.log("%d",  d - a);
           }
        }
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));