rtfcu trfcu rftcu frtcu tfrcu ftrcu rtcfu trcfu rctfu crtfu tcrfu ctrfu rfctu frctu rcftu crftu fcrtu cfrtu tfcru ftcru tcfru ctfru fctru cftru rtfuc trfuc rftuc frtuc tfruc ftruc rtufc trufc rutfc urtfc turfc utrfc rfutc frutc ruftc urftc furtc ufrtc tfurc fturc tufrc utfrc futrc uftrc rtcuf trcuf rctuf crtuf tcruf ctruf rtucf trucf rutcf urtcf turcf utrcf rcutf crutf ructf urctf curtf ucrtf tcurf cturf tucrf utcrf cutrf uctrf rfcut frcut rcfut crfut fcrut cfrut rfuct fruct rufct urfct furct ufrct rcuft cruft rucft urcft curft ucrft fcurt cfurt fucrt ufcrt cufrt ucfrt tfcur ftcur tcfur ctfur fctur cftur tfucr ftucr tufcr utfcr futcr uftcr tcufr ctufr tucfr utcfr cutfr uctfr fcutr cfutr fuctr ufctr cuftr ucftr
Note: these 'words' (valid or invalid) are all the permutations of the word rtfcu. These words are obtained by scrambling the letters in rtfcu.