Compilare: user.cpp: In function ‘int main()’: user.cpp:21:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.size(); i++) ^ user.cpp:27:44: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < it.second.size(); i++) ^