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
soldier = input().split()
cost = int(soldier[0])
dollars = int(soldier[1])
bananas = int(soldier[2])

bananas_no = 0
b_list = []
total_cost = []
no_cost = 0
while bananas > bananas_no:
    bananas_no += 1
    b_list.append(bananas_no)

for x in b_list:
    formula = x*cost
    total_cost.append(formula)

total = 0
for d in total_cost:
    total += int(d)

c = total - dollars
if c > 0:
    print(c)
elif c < 0:
    print(no_cost)
else:
    print(no_cost)
