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: Wrong Answer)

#include <stdio.h>

int a[2] = { 0 };
int b[2] = { 0 };

void swap(int a, int b) {
	int tmp;
	tmp = a;
	a = b;
	b = a;
}

int main(void) {
	int ans = 0;

	scanf("%d %d %d %d", &a[0], &a[1], &b[0], &b[1]);
	if (a[0] > b[0]) {
		swap(a[0], b[0]);
		swap(a[1], b[1]);
	}

	if (b[0] < a[1]) {
		if (b[1] <= a[1]) ans = b[1] - b[0];
		else ans = a[1] - b[0];
	}

	printf("%d\n", ans);

	return 0;
}