oreo[4], sera[4], arso[4], osra[4], raso[4], rosa[4], eros[4], roso[4],
era[3], rea[3], aro[3], ora[3], ero[3], oro[3], osa[3], oso[3], ars[3], ras[3], sra[3], ser[3], ros[3],
eo[2], ar[2], er[2], re[2], or[2], ro[2], as[2], es[2], se[2], os[2],
