a-a a-b a-c aaa aab aac aau aax ab- aba abb abc abu abx ac- aca acb acc acu acx au- aua aub auc aux ax- axa axx b-u baa bab bac bau bax bba bbb bbc bbu bbx bca bcb bcc bcu bcx bua bub buc buu bux bxb bxx c-- caa cab cac cau cax cba cbb cbc cbu cbx cca ccb ccc ccu ccx cua cub cuc cuu cxc cxx ua- uaa uab uac uau uba ubb ubc ubu ubx uca ucb ucc ucu uua uuc uuu uxb uxc uxu xaa xac xau xbc xbx xcb xcx xxx