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
request = input()

list_request = request.split(" ")


def check_need(need_money, my_money):
    if int(my_money) >= need_money:
        return 0
    else:
        return need_money - int(my_money)
    
def how_much_to_pay(first_price, q):
    i = 1
    price = 0
    while i <= int(q):
        price = price + int(first_price) * i
        
        i += 1
    return price

print(check_need(how_much_to_pay(list_request[0], list_request[2]), list_request[1]))