serf sero serp serr sers sesc sese seso sess sfcc sfco sfcs sfdc sfer sffc sfor sfos sfpc sfpd sfrc sfro sfss soce soco socr socs sodd sode sodo sods soec soeo soep soes sofo sood soof soop soor soos sopd sope sopo sopp sops sord sore soro sorr sors sose soso soss spcc spco spcs spdc spde spdf spdp spdr spec sped spee spef sper spes spfc spfs spoc spod spoo spop spor spos sppd sppf spps sprd spro sprs spsd spse spso spsp spss srcc srde srec sreo sres srfc sros srpc srps srsd srsp sscc ssce sscp sscs ssdc ssdd ssdf ssdp ssec ssee ssep sses ssfc ssfp ssoc ssop sspc sspe sspf sspo ssps ssrc ssrs sssc sssf ssss