-up b-p b-u bbb bbo bbp bbs bbu bob boo bop bos bou bpb bpo bpp bps bpu bsb bso bsp bss bsu bub buo bup bus buu ob- obb obo obp obs obu oo- oob ooo oop oos op- opb opo opp ops os- osb oso osp oss osu ou- ouo oup ous p-p pbb pbo pbp pbs pbu pob poo pop pos pou ppb ppo ppp pps ppu ps- psb pso psp pss psu pub pup pus puu sbb sbo sbp sbs sbu sob soo sop sos sou spb spo spp sps spu ss- ssb sso ssp sss ssu sub suo sup sus suu ubb ubo ubp ubs ubu uob uoo uop uos up- upb upo upp ups upu usb uso usp uss usu uus uuu