#include <iostream>

template <typename T>
class Animal {
public:
    void speak() {
        static_cast<T*>(this)->sound();
    }
    void sound() {
        std::cout << "Ops!";
    }
};

class Cat : public Animal<Cat> {
public:
    void sound() {
        std::cout << "Meow!";
    }
};

class Dog : public Animal<Dog> {
};

int main() {
    Cat cat;
    cat.speak();
    Dog dog;
    dog.speak();
    return 0;
}

#include <iostream>

int main() {
  int a[3][3] = {
      {1, 2, 3},
      {4, 5, 6},
      {7, 8, 9}
  };
  int* aPtr = &a[1][1];
  std::cout << aPtr[0] 
            << aPtr[1] 
            << aPtr[2];
  return 0;
}

#include <iostream>

int main() {
    const int factors[6] = {4, 4, 7, 1, 7, 19};    
    int val = 0;

    for (int i = 0; i < 6; ++i) {
        val += factors[i];
        std::cout << val << " ";
    }
    
    return 0;
}