costs ocsts csots scots oscts socts cotss octss ctoss tcoss otcss tocss cstos sctos ctsos tcsos stcos tscos ostcs sotcs otscs toscs stocs tsocs cosst ocsst csost scost oscst socst cosst ocsst csost scost oscst socst cssot scsot cssot scsot sscot sscot ossct sosct ossct sosct ssoct ssoct cotss octss ctoss tcoss otcss tocss costs ocsts csots scots oscts socts ctsos tcsos cstos sctos tscos stcos otscs toscs ostcs sotcs tsocs stocs cstso sctso ctsso tcsso stcso tscso cssto scsto cssto scsto sscto sscto ctsso tcsso cstso sctso tscso stcso stsco tssco sstco sstco tssco stsco ostsc sotsc otssc tossc stosc tsosc osstc sostc osstc sostc ssotc ssotc otssc tossc ostsc sotsc tsosc stosc stsoc tssoc sstoc sstoc tssoc stsoc
Note: these 'words' (valid or invalid) are all the permutations of the word costs. These words are obtained by scrambling the letters in costs.