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 hgfdytkdcgh {

	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		int sum=0;
		int[]x=new int[3];
		for (int i=0;i<x.length;i++)
			x[i]=sc.nextInt();
		for (int j=0;j<x[2];j++) {
			
			sum+=x[0]*(j+1);
		}
		int y=sum-x[1];
		if (y<0)
			y=0;
		System.out.print(y);
			

	}

}
