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
num = input()
my_list = []
lst = []
my_list.append(num.split())
for i in my_list:
  new_list = i
k = int(new_list[0])
n = int(new_list[1])
w = int(new_list[2])
count = 0
for z in range(1, w+1):
  count = k*int(z)
  lst.append(count)
x = sum(lst)
a = x-n
if a > 0:
  print(a)
else:
  print("0")