-er ddd dde ddi ddp ddr ddx de- ded dee dei dep der dex di- did die dii dip dir dix dpd dpe dpi dpp dpr drd dre dri drp drr drx dxd dxi dxp dxr dxx ed- edd ede edi edp edr edx eed eee eep eer eex eid eie eii eip eir eix ep- epd epe epi epp epr epx erd ere eri erp err ex- exd exe exi exp exr exx i-d idd ide idi idp idr idx ie- ied iee iei iep ier iex iid iie iii iip iir iix ipd ipe ipi ipp ipr ipx ir- ird ire iri irp irr irx ixe ixi p-p pdd pde pdi pdp pdr pdx ped pee pei pep per pex pid pie pii pip pir pix ppd ppe ppi ppp ppr ppx prd pre pri prp prr prx pxe pxr rdd rde rdi rdp rdr rdx re- red ree rei rep rer rex rid rie rii rip rir rix rpd rpe rpi rpp rpr rpx rrd rri rrp rrr rxp rxr xde xdi xdr xed xee xep xer xex xie xii xix xpd xpe xpp xrd xrx xxi xxp xxx