Thanks so much vmpstr!
It works!!

The purpose of the Insert function is to add a new integer in the Heap assuming that it is not already full. If Heap capacity has been reached, it attempts to double the current capacity. If capacity cannot be doubled, it throws FullHeap.

Here is the Heap.h file
const int MAXSIZE = 4; // Default maximum heap size
class Heap // Smart Heap ADT as an array
{...