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 C (GCC 5.4.1) (judge verdict: Accepted)

        #include <stdio.h>
        #include <stdlib.h>
         
        int main() {
         
        	int num_a, num_b, num_c, num_d;
        	int max_s,min_e;
        	int res = 0;
         
        	scanf("%d %d %d %d", &num_a, &num_b, &num_c, &num_d);
         
        	max_s = (num_a > num_c) ? num_a : num_c;
         
        	min_e = (num_b < num_d) ? num_b : num_d;
         
        	res = min_e - max_s;
         
        	if (res < 0) {
        		printf("%d", 0);
        	} else {
        		printf("%d", res);
        	}
         
        	return 0;
         
        }