#include <iostream>

int main() {
    std::cout << "Hello world!" << std::endl;
    std::cout << " hello" << std :: cout <<"ff"<< std::endl;
    std::cout << " hello" << std:: cout <<". " << std::endl;
    std::cout << ". " << std::cout <<" " <<std::cout <<" " << std::endl;
    return 0;
}