Compilare: main.cpp: In function 'std::ostream& operator<<(std::ostream&, const Number&)': main.cpp:55:24: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 55 | for (auto i = 1; i < n.size(); i++) { | ~~^~~~~~~~~~