 At the end of the 9th century, one of these students of Methodius – Naum, who had settled in Preslav, Bulgaria – created the Cyrillic script, which almost entirely replaced Glagolitic during the Middle Ages.The Cyrillic alphabet is derived from the Greek alphabet, with some letters (like ⟨ш⟩, ⟨ц⟩, ⟨ч⟩, ⟨ъ⟩, ⟨ь⟩, ⟨ѣ⟩) peculiar to Slavic languages being derived from the Glagolitic alphabet.The decision in favor of Cyrillic created an alphabetical difference between the two literary centres of the Bulgarian state in Pliska and Ohrid.