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 os
import sys

#k,n,w

#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?

#k+2k+2(2k)+2(2)(2k)

# 2^(n)*k
# k*Sum(i=1; w)(i) - n =answer

t=sys.stdin.readline()
lines=[]
while t:
    lines.append(t.split(' '))
    t=sys.stdin.readline()

for line in lines:
    k=int(line[0]) # Value of first banana
    n=int(line[1]) # Dollars that the soldier has
    w=int(line[2]) # Bananas to buy
    suma=0
    for i in range(1,w+1):
        suma=suma+i*k
    
    result=suma-n
    if result>0:
        print(result)
    else:
        print(0)



