Angrapa
Originating in Lake Mamry , it joins the 101-km-long Instruch at a point near Chernyakhovsk – variously assessed as lying 140 , 169 , or 172 km from its source – to form the Pregolya . 
<triplet> Instruch <subj> Pregolya <obj> mouth of the watercourse <triplet> Pregolya <subj> Instruch <obj> origin of the watercourse