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
import sys
# from copy import deepcopy


def main():
    inp = sys.stdin.readlines()
    costs = int(inp[0].split(" ")[0])
    money = int(inp[0].split(" ")[1])
    wants = int(inp[0].split(" ")[2])

    to_pay = 0
    for banana in range(wants):
        to_pay = to_pay+(costs * (banana+1))

    to_borrow = money - to_pay

    if to_borrow > money or to_borrow > 0:
        print(0)
    else:
        print(abs(to_borrow))

main()
