Help me in solving FIZZBUZZ2304 problem

[roumak]

Why do I get a Runtime exception?

There are four types of Runtime exception, and you can see which one you are getting by hovering your mouse over the icon. You cannot know anything more specific; for example the exact Exception thrown in Java. Note that some errors could lead onto other errors, so even if you are getting one particular message, you should check each one separately.

Refer to this. It simply means that there is some error in the code, which is occurring in some specific test cases.