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
"""
> Get the 3 inputs
(number of bananas, price of bananas, money)

>compute the total price of banans
> subtract total price from money
> print
"""

inputs = [int(a) for a in input().strip().split(" ")]
price, money, num_banana = inputs[0], inputs[1], inputs[2]

total = 0
for x in range(1, num_banana+1):
    total += price*x

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