#include <iostream>
#include <string>
 
using namespace std;
int arr[10001];
int index;
 
void push(int number)
{
	arr[index] = number;
	index++;
}
int size()
{
	return index;
}
 
int top()
{
	return (!size()) ? -1 : arr[index - 1];
}
 
bool empty()
{
	return (!size()) ? true : false;
}
 
void pop()
{
	if (!size())
		cout << -1 << endl;
	else
	{
		cout << arr[index - 1] << endl;
		index--;
	}
}
int main(void)
{
	string com;		//명령어
	int num;		//push할 정수
	int n;			//테스트 케이스 수
	cin >> n;
 
	while (n--)
	{
		cin >> com;
 
		if ("push" == com)
		{
			cin >> num;		//push일 경우에만 정수 입력
			push(num);
		}
		else if ("top" == com)
			cout << top() << endl;
		else if ("size" == com)
			cout << size() << endl;
		else if ("empty" == com)
			cout << empty() << endl;
		else if ("pop" == com)
			pop();
	}
	return 0;
}

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14
push 1
push 2
top
size
empty
pop
pop
pop
size
empty
pop
push 3
empty
top