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
aa= input()
a=aa.split()
kk=a[0]
k=int(kk)
nn=a[1]
n=int(nn)
ww=a[2]
w=int(ww)
p=0
sum=0
if k>=1 or w<=1000 or p>=0 or p<=10**9:
    while p<=w:
        sum = sum+p*k
        p=p+1
    res = sum-n
    if res<0:
        print(0)
    else:
        print(res)

