#include <iostream>

using namespace std;

struct iStack
{
    int capacity;
    int top;
    int* data;

    void init(int capacity);
    void destroy();
    void push(int value);
    bool pop(int*);
};
bool iStack::pop(int* value)
{
    if (this->data != nullptr && this->top >= 0)
    {
        *value = this->data[this->top--];
        return true;
    }

    cout << "Something went wrong!" << endl;
    return false;

}

void iStack::push(int value)
{
    if (this->data != nullptr && this->top < this->capacity - 1)
    {
        this->data[++(this->top)] = value;
        return;
    }

        cout << "Error pushin value!";
    return;
}

void iStack::init(int capacity)
{
    this->capacity = capacity;
    this->top = -1;
    this->data = new int[capacity];
}

void iStack::destroy()
{
    delete[] this->data;
    this->data = nullptr;
    this->capacity = 0;
    this->top = -1;
}

int main()
{
    iStack stack;

    stack.init(3);

    stack.push(20);
    stack.push(30);
    stack.push(40);

    int value;

    stack.pop(&value);
    cout << value << endl;

    stack.pop(&value);
    cout << value << endl;

    stack.pop(&value);
    cout << value << endl;


    stack.destroy();

    return 0;
}