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

(x, y, z) = input ().split (" ")


costFirstBanana = int (x)
initialDollars  = int (y)
bananas         = int (z)

# calcula custo total das bananas

totalCost = 0

for i in range (0, bananas):
    
    if i == 0:
        
        totalCost += costFirstBanana
        
    else:
        
        totalCost += (i + 1) * costFirstBanana
        
        
if totalCost > initialDollars:
    
    print (totalCost - initialDollars) 
    
else:
    
    print (0)


    

# 1497030693174
