Compilare: main.cpp: In function 'bool check(std::string)': main.cpp:12:19: 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()-1;i++){ | ~^~~~~~~~~~~ main.cpp:21:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 21 | for(int i(0);i<s.size();i++){ | ~^~~~~~~~~