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
import java.util.Scanner;

public class Main {
    static Scanner sc = new Scanner(System.in);

    public static void main(String[] args) {
        int price = sc.nextInt();
        int money = sc.nextInt();
        int bananas = sc.nextInt();
        int priceC = 0;
        int borrow = 0;
        for (int i = 0; i < bananas; i++) {
            priceC = price * (i + 1);

            if ((money - priceC) >= 0) {
                money = money - priceC;
            } else {
                borrow = borrow + (priceC - money);
                money = 0;
            }
        }
        System.out.println(borrow);

    }
}