human
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
Solve the task in PYTHON.
 ... Can you provide a the Python program you requested?
assistant
#Here is the Python program you requested.

class SoldierBananas:
    def solve(self,first,soldier,bananas):
        cost=0
        increment=1
        for x in range(0,bananas):
            cost+=increment*first
            increment+=1
        if soldier<cost:
            return abs(soldier-cost)
        else: return 0
if __name__ == "__main__":
    first,soldier,bananas = map(int,raw_input().split(" "))
    sb = SoldierBananas()
    print sb.solve(first,soldier,bananas)