fff ffi ffk ffs fft fif fii fik fis fit fkf fki fkk fkt fsf fsi fsk fss fst ftf fti ftk fts ftt i-f iff ifi ifs ift iif iii iis iit ikf iki ikk iks ikt is- isf isi isk iss ist itf iti itk its itt k-t kff kfi kfs kif kii kik kis kit kki kkk kks kkt ksf ksi ksk kss kst ktf ktk kts ktt sff sfi sfk sfs sft sif sii sik sis sit sk- skf ski skk sks skt ss- ssf ssi ssk sss sst stf sti stk sts stt tff tfi tfk tfs tft tif tii tik tis tit tkk tks tkt tsf tsi tsk tss tst ttf tti ttk tts ttt