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
soldier = input()
a = []
count = 0
def get_the_list(count,limit,a):
    for i in range(0,len(limit)):
        if limit[i] == ' ':
            a.append(int(limit[int(count):int(i)]))
            count = i+1
        elif i == len(limit)-1:
            a.append(int(limit[int(count):len(limit)]))
    return a

data = get_the_list(count,soldier,a)

money = 0
counting = 1
while(counting<=data[2]):
    money += counting * data[0]
    counting+=1

if data[1]-money < 0:
    print(money-data[1])
else :
    print(0)



