Compilare: user.cpp: In function ‘std::vector<int> prod(const std::vector<int>&, const std::vector<int>&)’: user.cpp:78:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a.size(); i++) ^ user.cpp:80:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < b.size(); i++) ^ user.cpp: In function ‘int main()’: user.cpp:139:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < p.size(); i++) ^