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
class CodeforcesTask546ASolution:
    def __init__(self):
        self.result = ''
        self.k_n_w = []

    def read_input(self):
        self.k_n_w = [int(x) for x in input().split(" ")]

    def process_task(self):
        all_price = 0
        for x in range(self.k_n_w[2]):
            all_price += self.k_n_w[0] * (x + 1)
        missing = -(self.k_n_w[1] - all_price)
        self.result = str(max(0, missing))

    def get_result(self):
        return self.result


if __name__ == "__main__":
    Solution = CodeforcesTask546ASolution()
    Solution.read_input()
    Solution.process_task()
    print(Solution.get_result())
