Partial implemented interface in C++

main.cpp

#include <iostream>

using namespace std;

class Base {
  virtual void one() const = 0;
  virtual void two() const = 0;
};

class First : public Base {
  public:
  void one() const override {
    cout << "one" << endl;
  }
};

class Second : public First {
  public:
  void two() const override {
    cout << "two" << endl;
  };  
};


int main() {
  Second s;
  s.one();
  s.two();
}