What is an invalid use of a non-statistical data member?

Question

This is an error that appeared in one of my programs
https://code.sololearn.com/cSyMmDL3QZ2I/?ref=app

Answer 1

The size of static array should be known at compile time so to create variable at compile time, you need to use:
const static int XKPM = 0;
in your code at line 37.