prnub rpnub pnrub nprub rnpub nrpub prunb rpunb purnb uprnb rupnb urpnb pnurb npurb punrb upnrb nuprb unprb rnupb nrupb runpb urnpb nurpb unrpb prnbu rpnbu pnrbu nprbu rnpbu nrpbu prbnu rpbnu pbrnu bprnu rbpnu brpnu pnbru npbru pbnru bpnru nbpru bnpru rnbpu nrbpu rbnpu brnpu nbrpu bnrpu prubn rpubn purbn uprbn rupbn urpbn prbun rpbun pbrun bprun rbpun brpun pubrn upbrn pburn bpurn ubprn buprn rubpn urbpn rbupn brupn ubrpn burpn pnubr npubr punbr upnbr nupbr unpbr pnbur npbur pbnur bpnur nbpur bnpur pubnr upbnr pbunr bpunr ubpnr bupnr nubpr unbpr nbupr bnupr ubnpr bunpr rnubp nrubp runbp urnbp nurbp unrbp rnbup nrbup rbnup brnup nbrup bnrup rubnp urbnp rbunp brunp ubrnp burnp nubrp unbrp nburp bnurp ubnrp bunrp
Note: these 'words' (valid or invalid) are all the permutations of the word prnub. These words are obtained by scrambling the letters in prnub.