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 main(void)
{
	int A,B,C,D;
	int bc,da,dc,ba;
			
	scanf("%d%d%d%d",&A,&B,&C,&D);
	
	if(A < B && C < D)
	{
		if(A< B && C < D && B < C)
		{
			printf("0\n");
		}
		else if(A< B && C < D && D < A)
		{
			printf("0\n");
		}
		
		else if(A < C && B < D && C < B)
		{
			bc = B - C;
			printf("%d\n",bc);
		}
		else if(C < A && B < D && A < D)
		{
			da = D - A;
			printf("%d\n",da);
		}
		else if(A < C && D < B)
		{
			dc = D - C;
			printf("%d\n",dc);
		}
		else if(C < A && B < D)
		{
			ba = B - A;
			printf("%d\n",ba);
		}
	}
	else
	{
		printf("エラー");
	}
	
	return 0;
}