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 SoldierAndBananas {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int k, n, w;
        k = scan.nextInt();
        n = scan.nextInt();
        w = scan.nextInt();
        System.out.println(bananas(k, n, w));
        scan.close();
    }

    static int bananas(int k, int n, int w) {
        int total = 0;
        for (int i = 0; i < w; i++) {
            total = total + (k * (i + 1));
        }
        return  (total - n < 0) ? 0 : total - n;
    }
}
