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
inputs=input()
inputs=inputs.split(" ")

each_banana_money,initial_money,banana_want=inputs if len(inputs)==3 else False

each_banana_money=int(each_banana_money)
initial_money=int(initial_money)
banana_want=int(banana_want)

requireMoney=0
while int(banana_want)!=0:
    requireMoney=requireMoney+(banana_want*each_banana_money)
    banana_want-=1

result=requireMoney-initial_money
if result < 0 : print(0)
else : print(result)

