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
data = input()
start_cost, start_money, need_to_buy = data.split()

def count_additional_funds(banana_cost, money, need_to_buy):
    count = 0
    while need_to_buy > 0:
        count += need_to_buy
        need_to_buy -= 1
    additional_funds = money - (banana_cost * count)
    return -additional_funds if additional_funds < 0 else 0

print(count_additional_funds(int(start_cost), int(start_money), int(need_to_buy)))
