Two brothers sold a flock of sheep. For each sheep, they received as many dollars as the total number of sheep in the original flock. The money was divided as follows: The older brother took 10 dollars, after which the younger brother took 10 dollars. This process repeated until it was the younger brothers turn and there wasn't a full 10 dollars left. He took what remained, and in order to even things up, the old brother gave him a penknife. What was the penknife worth?