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
input_list = []
num = 0

while True:
    if num == 1:
        break
    line = input()
    line = line.split()
    line = list(map(int, line))
    # input_list.append(line)
    num += 1

# input_list.__delitem__(0)

count = 1
cost = 0
for banana in range(line[2]):
    x = line[0] * count
    count += 1
    cost += x

if cost > line[1]:
    print(cost - line[1])
else:
    print(0)
