#include <iostream>
using namespace std;
const int MAXSTACKSIZE=50;
template <typename T>
class bstack
{
	public:
		bstack()
		{
//		 T stacklist[MAXSTACKSIZE];
			 topIndex=-1;
		}

	    void push(const T& item)
		{  
			if(!full())
			{
				topIndex++;
				stacklist[topIndex]=item;
			}
			else
				cout<<"overflowError"<<endl;
		}
		void pop()
		{  if(!empty())
			 topIndex--;
		   else 
			 cout<<"underflowError"<<endl;
		}

		T& top()
		{  
			if(!empty())			
			   return stacklist[topIndex];			
			else
		       cout<<"underflowError"<<endl;
		}
		const T& top() const
		{
		if(!empty())			
			   return stacklist[topIndex];			
			else
		       cout<<"underflowError"<<endl;
		}
		bool empty() const
		{ 
			if(topIndex==-1)
				return  true;
			else 
				return false;
		}
		int size() const
		{
			return (topIndex+1);
		}
		bool full()const
		{
			if(topIndex==MAXSTACKSIZE)
				return true;
			else 
				return false;
		}
	private:
		T stacklist[MAXSTACKSIZE];
		int topIndex;

};