hadst ahdst hdast dhast adhst dahst hasdt ahsdt hsadt shadt ashdt sahdt hdsat dhsat hsdat shdat dshat sdhat adsht dasht asdht sadht dsaht sdaht hadts ahdts hdats dhats adhts dahts hatds ahtds htads thads athds tahds hdtas dhtas htdas thdas dthas tdhas adths daths atdhs tadhs dtahs tdahs hastd ahstd hsatd shatd ashtd sahtd hatsd ahtsd htasd thasd athsd tahsd hstad shtad htsad thsad sthad tshad asthd sathd atshd tashd stahd tsahd hdsta dhsta hsdta shdta dshta sdhta hdtsa dhtsa htdsa thdsa dthsa tdhsa hstda shtda htsda thsda sthda tshda dstha sdtha dtsha tdsha stdha tsdha adsth dasth asdth sadth dsath sdath adtsh datsh atdsh tadsh dtash tdash astdh satdh atsdh tasdh stadh tsadh dstah sdtah dtsah tdsah stdah tsdah
Note: these 'words' (valid or invalid) are all the permutations of the word hadst. These words are obtained by scrambling the letters in hadst.