c-- ccc cce ccf cck ccs ce- cec cee cef cek ces cfc cfe cff cfk cfs ckc cks csc cse csf csk css ec- ecc ece ecf eck ecs eec eee eef eek ees ef- efc efe eff efs ekc eke ekf eks es- esc ese esf esk ess fcc fce fcf fck fcs fec fee fef fek fes ffc ffe fff ffk ffs fkc fkf fkk fsc fse fsf fsk fss kcc kce kck kcs ke- kec kee kef kek kes kfc kff kfs kkc kke kkk kks ksc kse ksf ksk kss scc sce scf sck scs se- sec see sef sek ses sfc sfe sff sfk sfs sk- skc ske skf skk sks ss- ssc sse ssf ssk sss