#include <iostream>
#include <stack>

using namespace std;

class FIFO {
public:
    void push(int value) {
        main_stack.push(value);
    }

    int pop() {
        int result = 0;
        while (!main_stack.empty() && main_stack.size() > 1) {
            help_stack.push((int &&) main_stack.top());
            main_stack.pop();
        }
        result = main_stack.top();
        main_stack.pop();
        while (!help_stack.empty()) {
            main_stack.push((int &&) help_stack.top());
            help_stack.pop();
        }
        return result;
    }

    unsigned long size() {
        return this->main_stack.size();
    }

private:
    stack<int> main_stack;
    stack<int> help_stack;
};

int main() {
    FIFO fifo;
    fifo.push(4);
    fifo.push(3);
    fifo.push(2);
    fifo.push(1);
    cout << fifo.pop(); // Powinno wypisać 4
    fifo.push(4);
    fifo.push(3);
    fifo.push(2);
    fifo.push(1);
    cout << fifo.pop(); // Powinno wypisać 3 jeszcze z poprzedniego dodania
    return 0;
}