Motion vs. location in sitting and lying

Сљсть/садќться and лљчь/ложќться imply motion; therefore, the Accusative case (as in за стћл) is used after the relevant prepositions and the question-word кудђ is used (not гдљ) Compare:

— Кудђ ћн сљл? — На дивђн.	"Where did he sit down?" "On the couch."
— Гдљ ћн сидљл? — На дивђне.	"Where was he sitting?" "On the couch."
Ћн лёг на дивђн.	He lied down on a couch.
Ћн лежђл на дивђне.	He was lying on a couch.