a-a a-b a-c aaa aab aac aap aar ab- aba abb abc abp abr ac- aca acb acc acp acr ap- apa apb apc app apr ar- ara arb arc arp arr b-p baa bab bac bap bar bba bbb bbc bbp bbr bca bcb bcc bcp bcr bpa bpb bpc bpp bpr bra brb brp brr c-- caa cab cac cap car cba cbb cbc cbp cbr cca ccb ccc ccp ccr cpa cpb cpc cpp cpr cra crb crc crp crr p-p paa pab pac pap par pba pbb pbc pbp pbr pca pcb pcc pcp pcr ppa ppb ppc ppp ppr pra prb prc prp prr ra- raa rab rac rap rar rba rbb rbc rbp rbr rca rcb rcc rcp rcr rpa rpb rpc rpp rpr rra rrb rrc rrp rrr