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
from sys import stdin,stdout

def main():
    inp = [int (i) for i in input().split(" ")]
    money = inp[1] 
    pay = 0
    for i in range (1,inp[2]+1):
        pay = pay + (i * inp[0])
    hutang = pay - money

    if hutang >= 0:
        print(hutang)
    else:
        print(0)
  
if __name__ == "__main__":
    main()
