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
def main():
    data = input().split()
    nums = list()
    amount = int(data[0])
    summ = 0
    for x in range(int(data[2])):
        summ += int(data[0])
        nums.append(summ)

    for n in range(len(nums) - 1):
        amount+=nums[n + 1]

    if(amount > int(data[1])):
        print(abs(amount - int(data[1])))
    else:
        print(0)
    
    
if __name__ == "__main__":
    main()
