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
list1=list(map(int,input().split()))
l1=list1[0]
l2=list1[1]
l3=list1[2]
newList=[]
for i in range(1,l3+1):
    newList.append(i*l1)
sumList=sum(newList)
if sumList<=l2:
    print(0)
else:
    print(sumList-l2)
