a-a a-b a-c aaa aab aac aak aas aau ab- aba abb abc abk abs abu ac- aca acb acc ack acs acu aka akb akc akk aks aku as- asa asb asc ask ass asu au- aua aub auc auk aus b-u baa bab bac bak bas bau bba bbb bbc bbk bbs bbu bca bcb bcc bck bcs bcu bka bkb bkc bkk bks bsa bsb bsc bsk bss bsu bua bub buc buk bus buu c-- caa cab cac cak cas cau cba cbb cbc cbk cbs cbu cca ccb ccc cck ccs ccu cka ckb ckc cks csa csb csc csk css csu cua cub cuc cuk cus cuu ka- kaa kab kac kak kas kau kba kbb kbc kbk kbs kbu kca kcb kcc kck kcs kcu kkb kkc kkk kks kku ksa ksb ksc ksk kss ksu kub kuc kuk kus kuu saa sab sac sak sas sau sba sbb sbc sbk sbs sbu sca scb scc sck scs scu sk- ska skb skc skk sks sku ss- ssa ssb ssc ssk sss ssu sua sub suc suk sus suu ua- uaa uab uac uak uas uau uba ubb ubc ubk ubs ubu uca ucb ucc uck ucs ucu uka ukb ukc ukk uku usa usb usc usk uss usu uua uuc uus uuu