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
def find_loan(price,money_left,bananas):
    total_price = 0
    for i in range(bananas):
        total_price = total_price+price*(i+1)
    if total_price<=money_left:
        result = 0
    else:
        result =total_price-money_left
    return result



if __name__ =='__main__':
    a,b,c = map(int,input(" ").split())
    print(find_loan(a,b,c))