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
# first banana , number of $$ he has, bananas he wants
#bananas increment at k*i value meaning the second banana is 2 times the original price
n = [int(s) for s in input().split()]
total = 0
for index in range(1, n[2]+1):
    total += n[0]*index


print(total- n[1] if total-n[1]>0 else 0)

# 3 17 4
#he has to borrow: $13

#1 2 1
# 0