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
k1,n1,w1=input().split()
k=int(k1)
n=int(n1)
m=n
w=int(w1)
mused=0
count=1
p=0
i=w
while i>0:
    mused=count*k
    n=n-mused
    i=i-1
    count=count+1


if n<0:
    print(-1*n)
else:
    print('0')
