Compilare: main.cpp: In function 'bool ok(int)': main.cpp:13:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 13 | for (int i = 1; i < b.size(); i++) | ~~^~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:28:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 28 | for (i = 0; i < s.size(); i++) | ~~^~~~~~~~~~