A soldier wants to buy w bananas in the shop. He has to pay k dollars for the first banana, 2k dollars for the second one and so on (in other words, he has to pay i·k dollars for the i-th banana). 

He has n dollars. How many dollars does he have to borrow from his friend soldier to buy w bananas?

Input

The first line contains three positive integers k, 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, output 0.

Examples

Input

3 17 4


Output

13
def soldierAndBananas(cost, money, bananas):
    final_cost = 0
    for i in range(bananas):
        final_cost = final_cost + ((i + 1) * cost)
    if final_cost < money:
        print(0)
    else:
        print(final_cost - money)

cost, money, bananas = raw_input().split()

soldierAndBananas(int(cost), int(money), int(bananas))