-er b-u bbb bbe bbk bbr bbs bbu be- beb bee bek ber bes beu bkb bke bkk bkr bks brb bre brk brr brs bru bsb bse bsk bsr bss bsu bub bue buk bur bus buu ebb ebe ebk ebr ebs ebu eeb eee eek eer ees ekb eke ekr eks eku erb ere erk err ers eru es- esb ese esk esr ess esu eu- eub eue eur eus kbb kbe kbk kbr kbs kbu ke- keb kee kek ker kes kkb kke kkk kkr kks kku krk krr krs kru ksb kse ksk ksr kss ksu kub kue kuk kur kus kuu rbb rbe rbk rbr rbs rbu re- reb ree rek rer res reu rkb rke rkk rks rku rrb rrk rrr rrs rru rsb rse rsk rsr rss rsu rub rue ruk rur rus ruu sbb sbe sbk sbr sbs sbu se- seb see sek ser ses seu sk- skb ske skk skr sks sku sr- srb sre srk srr srs ss- ssb sse ssk ssr sss ssu sub sue suk sur sus suu ubb ube ubk ubr ubs ubu ueb uee uer ues ukb uke ukk ukr uku ur- urb ure urk urr urs uru usb use usk usr uss usu uue uur uus uuu