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 SolnB {

	public static void main(String[] args) {

		Scanner input = new Scanner(System.in);

		int a[] = new int[3];

		for (int i = 0; i < 3; i++)
			a[i] = input.nextInt();

		int s = 0;

		for (int i = 1; i <= a[2]; i++) {
			s += i * a[0];

		}

		if(s-a[1]<0) {
			System.out.println("0");
		}
		else {
			System.out.println(s-a[1]);
		}
	}

}
