#include <iostream>

using namespace std;

class Singleton {
    Singleton() {}
public:
    // Copy construction and assignment is disabled;
    Singleton(Singleton &other) = delete;
    void operator=(const Singleton &) = delete;

    static Singleton& get_instance() {
        static Singleton s;
        return s;
    }

    void f() {
        cout << "Singleton::f()" << endl;
    }
};

int main() {
    Singleton::get_instance().f();
}