a-a a-b a-i aaa aab aai aap aar aas ab- aba abb abi abp abr abs ai- aia aib aii aip air ais ap- apa apb api app apr aps ar- ara arb ari arp arr ars as- asa asb asi asp asr ass b-p baa bab bai bap bar bas bba bbb bbi bbp bbr bbs bi- bia bib bii bip bir bis bpa bpb bpi bpp bpr bps bra brb bri brp brr brs bsa bsb bsi bsp bsr bss ia- iaa iab iai iap iar ias iba ibb ibi ibp ibr ibs iia iib iii iip iir iis ipa ipb ipi ipp ipr ips ir- ira irb iri irp irr irs is- isa isb isi isp isr iss p-p paa pab pai pap par pas pba pbb pbi pbp pbr pbs pia pib pii pip pir pis ppa ppb ppi ppp ppr pps pra prb pri prp prr prs ps- psa psb psi psp psr pss ra- raa rab rai rap rar ras rba rbb rbi rbp rbr rbs ria rib rii rip rir ris rpa rpb rpi rpp rpr rps rra rrb rri rrp rrr rrs rsa rsb rsi rsp rsr rss saa sab sai sap sar sas sba sbb sbi sbp sbr sbs sia sib sii sip sir sis spa spb spi spp spr sps sr- sra srb sri srp srr srs ss- ssa ssb ssi ssp ssr sss