Compilare: main.cpp: In function 'std::__cxx11::string produs(int, std::__cxx11::string)': main.cpp:14:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a.size(); i++) { ~~^~~~~~~~~~ main.cpp:15:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < b.size(); j++) { ~~^~~~~~~~~~ main.cpp:20:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a.size() + b.size() - 1; i++) { ~~^~~~~~~~~~~~~~~~~~~~~~~~~ main.cpp: In function 'std::__cxx11::string suma(std::__cxx11::string, std::__cxx11::string)': main.cpp:39:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a.size(); i++) { ~~^~~~~~~~~~