#include <iostream>
#include <limits>
using namespace std;

template <class T>
class Stack {
    T* element;
    int length;
    int stackTop;

    const T INF = std::numeric_limits<T>::max();

public:
    Stack(int l) {
        stackTop = -1;
        length = l;
        element = new T[l];
    }

    ~Stack() {
        delete[] element;
    }

    T& top() { 
        if (stackTop == -1) throw std::invalid_argument("No Top Element.");
        return element[stackTop];
    }

    void pop() {
        if (stackTop == -1) throw std::invalid_argument("No Top Element.");
        stackTop--;
    }

    void push(const T& e) {
        if (stackTop == length - 1) {
            T* tmp = new T[2 * length];
            for (int i = 0; i < length; i++) {
                tmp[i] = element[i];
            }
            delete[] element;
            element = tmp;
            length *= 2;
        }
        stackTop++;
        element[stackTop] = e;
    }

    bool empty() const {
        return stackTop == -1;
    }
};

int main() {
    int n;
    cin >> n;
    Stack<int> s(n);

    for (int i = 0; i < n; i++) {
        int p;
        cin >> p;
        switch (p) {
            case 0: {
                if (!s.empty()) {
                    cout << s.top() << endl;
                    s.pop();
                } else {
                    cout << "invalid" << endl;
                }
                break;
            }
            case 1: {
                int val;
                cin >> val;
                s.push(val);
                break;
            }
            default:
                return 0;
        }
    }
    return 0;
}