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
#CodeForces
#Soldir and Bananas 
#Python 3.6.5

import sys
user_input = input()
user_input = user_input.split()
user_input = [int(f) for f in user_input]

k = user_input[0]
n = user_input[1]
w = user_input[2]

totalCost = 0
count = 1 
while(w > 0):
    totalCost += k * (count)
    count += 1
    w -= 1

if(totalCost < n):
    print(0)
else:
    print(abs(totalCost - n))
