Compilare: main.cpp: In function 'bool check(int)': main.cpp:6:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 6 | if (x>=0 && x<s.size()) | ~^~~~~~~~~ main.cpp: In function 'int main()': main.cpp:41:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 41 | for (int i=0; i<s.size(); i++) { | ~^~~~~~~~~