The Genitive case is used after certain prepositions:
Попросќте у Мђши стакђн.	Ask Masha for a glass.
У Мђши љсть стакђн?	Does Masha have a glass?
Вћт письмћ от Мђши.	Here's a letter from Masha.
Вћт письмћ из МосквІ.	Here's a letter from Moscow.
салђт из фрџктов	a fruit salad (i.e. 'a salad made from fruit')