Original: Its largest tributary is the Kunar river, which starts out as the Mastuj River, flowing from the Chiantar glacier in Chitral, Pakistan and once it flows south into Afghanistan it is met by the Bashgal river flowing from Nurestan.
Simplified: Its largest tributary is the Kunar River, which starts out as the Mastuj River, flowing from the Chiantar glacier in Chitral, Pakistan and once it flows south into Afghanistan it is met by the Bashgal river flowing from Nurestan.