A soldier wants to buyw bananas in the shop. He has to payk dollars for the first banana,2k dollars for the second one and so on (in other words, he has to payi·k dollars for thei-th banana).
He hasn dollars. How many dollars does he have to borrow from his friend soldier to buyw bananas?
Input
The first line contains three positive integersk, n, w (1 ≤ k, w ≤ 1000,0 ≤ n ≤ 109), the cost of the first banana, initial number of dollars the soldier has and number of bananas he wants.
Output
Output one integer — the amount of dollars that the soldier must borrow from his friend. If he doesn't have to borrow money, output0.