#include <cstdio>
#include <iostream>
#include <string>
#include <stack>
using namespace std;

stack<int> s;
void push(int num) {
    s.push(num);
}

void top() {
    if(s.empty()) printf("-1\n");
    else printf("%d\n", s.top());
}

void size() {
    printf("%d\n", s.size());
}

void empty() {
    if(s.empty()) printf("1\n");
    else printf("0\n");
}

void pop() {
    if(s.empty()) printf("-1\n");
    else {
        top();
        s.pop();
    }
}

int main(void)
{
    int n;
    scanf("%d", &n);

    while(n--) {
        string order;
        cin >> order;

        if(order == "push") {
            int num;
            scanf("%d", &num);

            push(num);
        }
        else if(order == "pop") pop();
        else if(order == "top") top();
        else if(order == "size") size();
        else if(order == "empty") empty();
    }
}