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 soldier_and_bananas(cost_banana, initial_dollars, no_bananas):
    total_cost_banana = 0
    for i in range(1, no_bananas + 1):
        total_cost_banana += i * cost_banana
    if total_cost_banana > initial_dollars:
        print(total_cost_banana - initial_dollars)
    else:
        print(0)


cost_banana, initial_dollars, no_bananas = map(int, input().split())
soldier_and_bananas(cost_banana, initial_dollars, no_bananas)
