a-a a-b a-c aaa aab aac aao aap aas ab- aba abb abc abo abp abs ac- aca acb acc aco acp acs aoa aob aoc aoo aop aos ap- apa apb apc apo app aps as- asa asb asc aso asp ass b-p baa bab bac bao bap bas bba bbb bbc bbo bbp bbs bca bcb bcc bco bcp bcs boa bob boc boo bop bos bpa bpb bpc bpo bpp bps bsa bsb bsc bso bsp bss c-- caa cab cac cao cap cas cba cbb cbc cbo cbp cbs cca ccb ccc cco ccp ccs co- coa cob coc coo cop cos cpa cpb cpc cpo cpp cps csa csb csc cso csp css oaa oab oac oao oap oas ob- oba obb obc obo obp obs oc- oca ocb occ oco ocp ocs oo- ooa oob ooc ooo oop oos op- opa opb opc opo opp ops os- osa osb osc oso osp oss p-p paa pab pac pao pap pas pba pbb pbc pbo pbp pbs pca pcb pcc pco pcp pcs poa pob poc poo pop pos ppa ppb ppc ppo ppp pps ps- psa psb psc pso psp pss saa sab sac sao sap sas sba sbb sbc sbo sbp sbs sca scb scc sco scp scs soa sob soc soo sop sos spa spb spc spo spp sps ss- ssa ssb ssc sso ssp sss