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 \leq A
• $0 \leq C
• 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.

0 75 25 100

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.

0 33 66 99

0

Alice and Bob were not holding their buttons at the same time, so the answer is zero seconds.

10 90 20 80

60