Compilare: user.cpp: In member function ‘void InputReader::advance()’: user.cpp:66:52: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(buffer, BUFFER_SIZE, 1, file); ^ user.cpp: In constructor ‘InputReader::InputReader(const char*)’: user.cpp:39:48: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(buffer, BUFFER_SIZE, 1, file); ^ user.cpp: In function ‘int main()’: user.cpp:117:12: warning: ‘res’ may be used uninitialized in this function [-Wmaybe-uninitialized] out << res << '\n'; ^