Polish, like other Slavic languages, permits complex consonant clusters, which often arose from the disappearance of yers (see § Historical development above). Polish can have word-initial and word-medial clusters of up to four consonants, whereas word-final clusters can have up to five consonants. Examples of such clusters can be found in words such as "bezwzględny" ('absolute' or 'heartless', 'ruthless'), "źdźbło" ('blade of grass'), ('shock'), and "krnąbrność" ('disobedience'). A popular Polish tongue-twister (from a verse by Jan Brzechwa) is ('In Szczebrzeszyn a beetle buzzes in the reed').