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
base_price, dengi, banans_to_buy = map(int, input().split())
money = 0

for i in range(banans_to_buy):
    # print('i:',i)
    if i == 0:
        money = base_price
        # print('Стоимость банана:', base_price, 'Потрачено денег:', money)
    else:
        money = money + base_price * (i+1)
        # print('Стоимость банана:', base_price * (i+1), 'Потрачено денег:', money)

if money > dengi:
    print(money-dengi)
else:
    print(0)