Compilare: main.cpp: In function 'int main()': main.cpp:14:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 14 | for (int i = 0; i < a.size(); ++i) | ~~^~~~~~~~~~ main.cpp:21:23: 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 < a.size(); ++i) | ~~^~~~~~~~~~ main.cpp:27:30: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 27 | for (int i = a.size(); i < b.size(); ++i) | ~~^~~~~~~~~~