#include <iostream>
using namespace std;
class PriorityQueue
{
private:
	int* arr;
	int sz;

	void up(int i)
	{
		while (i != 0 && arr[i] > arr[(i - 1) / 2])
		{
			swap(arr[i], arr[(i - 1) / 2]);
			i = (i - 1) / 2;
		}
	}

	void down(int i)
	{
		while (i < sz / 2)
		{
			int maxI = 2 * i + 1;
			if (2 * i + 2 < sz && arr[2 * i + 2] > arr[2 * i + 1])
				maxI = 2 * i + 2;
			if (arr[i] >= arr[maxI])
				return;
			swap(arr[i], arr[maxI]);
			i = maxI;
		}
	}

public:

	PriorityQueue(int k)
	{
		sz = 0;
		arr = new int[k];
	}

	~PriorityQueue()
	{
		delete arr;
	}
	void push(int value)
	{
		arr[sz++] = value;
		up(sz - 1);

	}

	void pop()
	{
		if (sz > 0)
		{
			swap(arr[0], arr[--sz]);
			down(0);

		}
		else
			return;
	}

	bool empty()
	{
		return sz == 0;
	}

	const int& top()
	{
		return arr[0];
	}

	int size()
	{
		return sz;
	}

};

void error_msg(bool check)
{
	if (!check)
		cout << "Error occured\n";
}

int main()
{
	PriorityQueue Q(10);
	Q.push(1); Q.push(4);
	Q.push(2); Q.push(8);
	cout << Q.size();
	error_msg(Q.size() == 4);
	error_msg(Q.top() == 8);
	Q.pop();
	cout << Q.size();
	error_msg(Q.top() == 4);
	Q.pop();
	cout << Q.size();
	error_msg(Q.top() == 2);
	Q.pop();
	cout << Q.size();
	error_msg(Q.top() == 1);
	Q.pop();
	cout << Q.size();
	error_msg(Q.empty());

}