bbb bbi bbs bby bi- bib bii bis biv biy bsb bsi bss bsv bsy bvb bvi bvs bvv by- byi bys i-v ibb ibi ibs ibv iby iib iii iis is- isb isi iss isv isy ivb ivi ivs ivv ivy iys iyy sbb sbi sbs sbv sby sib sii sis siv ss- ssb ssi sss ssv svb svi svs svv svy sy- syb syi sys vbi vbs vbv vi- vib vii vis viv viy vsb vsi vss vsv vvb vvi vvs vvv ybi ybs yby yii yis ysb ysi yss ysy yvi yvy yyb yys yyy