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.io.*;

public class Sample
{
	public static void main(String args[]) throws IOException
	{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String input[] = br.readLine().split(" ");
		int initial_cost = Integer.parseInt(input[0]);
		int money_have = Integer.parseInt(input[1]);
		int quantity = Integer.parseInt(input[2]);
		int total = 0;

		for(int i=1; i<=quantity; i++)
		{
			total = total + initial_cost * i;
		}

		if(total <= money_have)
				System.out.println(0);
		else
			System.out.println(total - money_have);
		br.close();

	}
}