public override FingerTree <WeightedElement <T>, double> Merge(FingerTree <WeightedElement <T>, double> f)
{
if (!(f is PriorityQueue <T>))
{
throw new Exception("oops");
}
return(new PriorityQueue <T>(_finger.Merge(((PriorityQueue <T>)f)._finger)));
}
public override FingerTree <SizedElement <T>, int> Merge(FingerTree <SizedElement <T>, int> f) => _finger.Merge(f);