Compilare: main.cpp: In function 'int main()': main.cpp:52:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 52 | for(int i = 0; i < s.length(); ++ i) | ~~^~~~~~~~~~~~ main.cpp:51:13: warning: unused variable 'st' [-Wunused-variable] 51 | int st = 0, dr = s.length() - 1; | ^~ main.cpp:51:21: warning: unused variable 'dr' [-Wunused-variable] 51 | int st = 0, dr = s.length() - 1; | ^~