1-2-3-4-5-6-7-8-9-0-1-2- D-----B---B---D-D-D--B-B; 1-2-3-4-5-6-7-8-9-0-1-2- D-tktkB-tkB-tkD-D-D--B-B; 1-2-3-4-5-6-7-8-9-0-1-2- D-tktkB-tkB-tkDtDtDttBtB; k k kk k