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
set_input = [int(x) for x in input().split(" ")]
base_cost = set_input[0]
current_money = set_input[1]
bananas_required = set_input[2]

total_cost = 0

for x in range(1, bananas_required + 1):
    total_cost += base_cost * x

if total_cost > current_money:
    print(total_cost - current_money)
else:
    print("0")
