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
inp = str(input())

vals=inp.split(" ")

cost = int(vals[0])
money_have = int(vals[1])
no_of_banana = int(vals[2])

total_cost = int(0)
initial_cost = cost
for n in range((no_of_banana)):
    cost = initial_cost*(n+1)
    total_cost = total_cost + (cost)
if int(total_cost-money_have) < 1:
    print("0")
else:
        print(int(total_cost-money_have))
