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
A,B,C = input("").split()
W = int(A)
R = int(B)
S = int(C)
T = [0]
Y = 0
X = 1
while Y != S:
    F = W*X
    T.append(F)
    Y = Y+1
    X = X+1

Q = sum(T)
Z = Q-R

if Z < 0:
    print("0")
else :
    print(Z)
   	  	  	 	 	  					 			   	 	