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>

void pria(int a, int b, int c, int d);
void prib();
void pric(int c, int d);
void prid(int a, int b, int c, int d);

int main()
{
	int a, b, c, d;
	while (scanf("%d%d%d%d", &a, &b, &c, &d)!=EOF) {
		if (a<=c) {
			if (c<b&&d>=b) pria(a, b, c, d);
			else if (c>=b) prib();
			else pric(c, d);	
		}
		else {
			if (a<d&&b>=d) prid(a, b, c, d);
			else if (a>=d) prib();
			else printf("%d", b-a);
		}
	}
	return 0;
}

void pria(int a, int b, int c, int d)
{
	printf("%d\n\n", b-c);
	printf("Alice started holding down her button %d second after the start-up of the robot, and released her button %d second after the start-up.\n", a, b);
	printf("Bob started holding down his button %d second after the start-up, and released his button %d second after the start-up.\n", c, d);
	printf("Therefore, the time when both of them were holding down their buttons, is the %d seconds from %d seconds after the start-up to %d seconds after the start-up.\n", b-c, c, b);
}

void prib()
{
	printf("0\n\n");
	printf("Alice and Bob were not holding their buttons at the same time, so the answer is zero seconds.\n");
}

void pric(int c, int d)
{
	printf("%d\n", d-c);
}

void prid(int a, int b, int c, int d)
{
	printf("%d\n\n", b-c);
	printf("Alice started holding down her button %d second after the start-up of the robot, and released her button %d second after the start-up.\n", a, b);
	printf("Bob started holding down his button %d second after the start-up, and released his button %d second after the start-up.\n", c, d);
	printf("Therefore, the time when both of them were holding down their buttons, is the %d seconds from %d seconds after the start-up to %d seconds after the start-up.\n", b-c, b, b);
}