Compilare: user.cpp: In function ‘std::vector<int> product(const std::vector<int>&, const std::vector<int>&)’: user.cpp:81:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (n < 2 * a.size() || n < 2 * b.size()) ^ user.cpp:81:47: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (n < 2 * a.size() || n < 2 * b.size()) ^ user.cpp:85:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a.size(); ++ i) ^ user.cpp:88:32: 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:138:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < C.size(); ++ i) ^ user.cpp: In constructor ‘InputReader::InputReader(const char*)’: user.cpp:15:47: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(buffer, SIZE, 1, input_file); ^ user.cpp: In member function ‘void InputReader::advance()’: user.cpp:37:51: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(buffer, SIZE, 1, input_file); ^