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 Banana {

		public static void main(String[] args) {
			// TODO Auto-generated method stub
			Scanner sc=new Scanner(System.in);
			int k=sc.nextInt();
			int d=sc.nextInt();
			int w=sc.nextInt();
			int c=0;
			for(int i=1;i<=w;i++)
				c+=i*k;
			if(c==d || c<d)
				System.out.println(0);
			else
				System.out.println(c-d);
		}

	}

