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
l=list(map(int,input().rstrip().split()))
a=l[0]
b=l[1]
c=l[2]
sum=0
for k in range(1,c+1):
		x=k*a
		sum=sum+x
y=sum-b
if(y>0):
	print(y)
else:
	print('0')
	
  	 	 		    				  	 	 	 	  	 		