ndsk dnsk nsdk sndk dsnk sdnk ndks dnks nkds knds dkns kdns nskd snkd nksd knsd sknd ksnd dskn sdkn dksn kdsn skdn ksdn
Note: these 'words' (valid or invalid) are all the permutations of the word ndsk. These words are obtained by scrambling the letters in ndsk.