Compilare: main.cpp: In function 'int main()': main.cpp:12:24: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 12 | for (int i=0; i<s.size();i++) { | ~^~~~~~~~~