irids riids iirds iirds riids irids irdis ridis idris diris rdiis driis iidrs iidrs idirs diirs idirs diirs ridis irdis rdiis driis idris diris irisd riisd iirsd iirsd riisd irisd irsid risid isrid sirid rsiid sriid iisrd iisrd isird siird isird siird risid irsid rsiid sriid isrid sirid irdsi ridsi idrsi dirsi rdisi drisi irsdi risdi isrdi sirdi rsidi sridi idsri disri isdri sidri dsiri sdiri rdsii drsii rsdii srdii dsrii sdrii iidsr iidsr idisr diisr idisr diisr iisdr iisdr isidr siidr isidr siidr idsir disir isdir sidir dsiir sdiir idsir disir isdir sidir dsiir sdiir ridsi irdsi rdisi drisi idrsi dirsi risdi irsdi rsidi sridi isrdi sirdi rdsii drsii rsdii srdii dsrii sdrii idsri disri isdri sidri dsiri sdiri
Note: these 'words' (valid or invalid) are all the permutations of the word irids. These words are obtained by scrambling the letters in irids.