sentence: Of the consonants , ㅊ chieut , ㅋ kieuk , ㅌ tieut , and ㅍ pieup are aspirated derivatives of ㅈ jieut , ㄱ giyeok , ㄷ digeut , and ㅂ bieup , respectively , formed by adding an extra stroke to the unaspirated letters .