Where did Kauṇḍinya, a Buddhist monk study?
Kaundinya: Kauṇḍinya (Sanskrit; Pali: "Koṇḍañña") also known as "Ājñātakauṇḍinya", Pali: "Añña Koṇḍañña") was a Buddhist monk follower of Gautama Buddha and the first to become an arhat. Gautama Buddha:  He is believed to have lived and taught mostly in the eastern part of ancient India sometime between the sixth and fourth centuries BCE.
in the eastern part of ancient India