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
first_banana, initial_money, num_bananas = input().split(" ")
first_banana=int(first_banana)
initial_money=int(initial_money)
num_bananas=int(num_bananas)
needed_money=0
def total_sum(w,k):
    i_banana = 0
    for i in range(w+1):
        i_banana+=i*k
    return i_banana
total=total_sum(num_bananas,first_banana)
total=int(total)
needed_money = total-initial_money
needed_money=int(needed_money)
if needed_money<0:
    print(0)
else:print(needed_money)