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
# for i in range(0, int(input())):
# 	arr = list(map(int, input().split()))
# 	count = 0
# 	if (all(arr[i] <= arr[i+1] for i in range(len(arr)-1))):
# 		print(0)
# 	else:
# a,b = map(int,(input().split()))
# count = 0
# while a <= b:
# 	a = a*3
# 	b = b*2
# 	count += 1
# print(count)
k,w,n = map(int, input().split())
price = 0
for i in range(1,n+1):
	price += i*k
if price-w <= 0:
	print(0)
else:
	print(price-w)