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

int arr[10001];
int idx = 0;

void push(int num) {
    arr[idx++] = num;
}

void top() {
    if(idx == 0) printf("-1\n");
    else printf("%d\n", arr[idx - 1]);
}

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

void empty() {
    if(idx == 0) printf("1\n");
    else printf("0\n");
}

void pop() {
    if(idx == 0) printf("-1\n");
    else {
        top();
        idx--;
    }
}

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();
    }
}