riser irser rsier srier isrer sirer riesr iresr reisr erisr iersr eirsr rseir sreir resir ersir serir esrir iserr sierr iesrr eisrr seirr esirr risre irsre rsire srire isrre sirre rirse irrse rrise rrise irrse rirse rsrie srrie rrsie rrsie srrie rsrie isrre sirre irsre risre srire rsire riers irers reirs erirs ierrs eirrs rires irres rries rries irres rires reris erris rreis rreis erris reris ierrs eirrs irers riers erirs reirs rseri sreri resri ersri serri esrri rsrei srrei rrsei rrsei srrei rsrei rersi errsi rresi rresi errsi rersi serri esrri sreri rseri ersri resri iserr sierr iesrr eisrr seirr esirr isrer sirer irser riser srier rsier iersr eirsr iresr riesr erisr reisr serir esrir sreir rseir ersir resir
Note: these 'words' (valid or invalid) are all the permutations of the word riser. These words are obtained by scrambling the letters in riser.