Compilare: user.cpp: In function ‘std::vector<int> combine(const std::vector<int>&, const std::vector<int>&)’: user.cpp:105:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (N < 2 * a.size() || N < 2 * b.size()) { ^ user.cpp:105:47: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (N < 2 * a.size() || N < 2 * b.size()) { ^ user.cpp:111:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a.size(); ++ i) ^ user.cpp:114:32: 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:173:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (w >= ans.size()) ^ user.cpp: In constructor ‘InputReader::InputReader(const char*)’: user.cpp:14:43: 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:36:47: 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); ^