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.IOException;
import java.util.Scanner;

public class cf {

	public static void main(String[] args) throws IOException {
		Scanner in = new Scanner(System.in);
		int k=in.nextInt(),n=in.nextInt(),w=in.nextInt();
		long a = ((w)*(w+1))/2;
		a *= k;
		 
		long dif = n-a;
		if(dif >= 0)
			System.out.println(0);
		else
			System.out.println(dif*(-1));
		
		

	}

}
