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
k,n,w = [int(x) for x in input().split()]
i = 1
s = 0
while(w!=0):
    p = i*k
    s = s + p
    i = i+1
    w = w-1
if((n>s) or (n==s)):
    a = 0
    print(a)
else:
    a = n-s
    d = abs(a)
    print(d)
    

    
    

    


        
    
    
            

    
    
    
    
    
    
    
    
    
