Compilare: user.cpp: In function ‘void back(int)’: user.cpp:48:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0 ;i < v[k].size(); i++) ^ user.cpp:55:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < v[k].size(); i++) ^ user.cpp: In function ‘int main()’: user.cpp:76:13: warning: unused variable ‘rad’ [-Wunused-variable] int rad = sqrt (x); ^ 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); ^