Compilare: user.cpp: In function ‘void back(int)’: user.cpp:51:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < v[k].size(); i++) ^ user.cpp:54:55: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0 ; j < fp[v[k][i]].size(); j++) ^ user.cpp:58:54: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < fp[v[k][i]].size(); j++) ^ user.cpp: In constructor ‘InputReader::InputReader(const char*)’: user.cpp:13:47: 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:35:51: 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); ^