#include <iostream>
#include <string>

template <typename T>
class Stack {
private:
	T *data; // 데이터 배열(arr)
	int capacity; // 스택의 크기
	int top_idx; // 스택 맨 위 인덱스 = 제일 최근 인덱스
	
public:
	//생성자
	Stack(int capacity = 1000) : data(new T[capacity]), capacity(capacity), top_idx(-1) {}
	
	//소멸자
	~Stack() {delete[] data;}
	
	void push(T value) {
		if(!is_full())
			this->data[++(this->top_idx)] = value;
		else
			std::cout << "Stack is full." << std::endl;
	}
	
	T pop() {
		if(this->top_idx != -1)
			return this->data[(this->top_idx)--];
		else
			return this->top_idx; //std::cout << "Stack is empty." << std::endl;
	}
	
	int size() {
		return (this->top_idx)+1;
	}
	
	bool is_empty() {
		return (this->top_idx == -1) ? true : false;
	}
	
	T top() {
		return (this->top_idx == -1) ? -1 : this->data[this->top_idx];
	}
	
	bool is_full() {
		return (this->top_idx == this->capacity) ? true : false;
	}
};


int main() {
	std::ios::sync_with_stdio(false);
	std::cin.tie(NULL); 
	std::cout.tie(NULL);
	
	int n;
	std::string op;
	Stack<int> stack;
	
	std::cin >> n;
	
	for (int i = 0; i < n; ++i) {
		std::cin >> op;
		
		if (op == "push") {
			int value;
			std::cin >> value;
			stack.push(value);
		}
		else if (op == "pop")
			std::cout << stack.pop() << '\n';
		else if (op == "size")
			std::cout << stack.size() << '\n';
		else if (op == "empty")
			std::cout << stack.is_empty() << '\n';
		else if (op == "top")
			std::cout << stack.top() << '\n';
	}
    
    return 0;
}