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 Main {
 public static void main(String args[]){
	 
	 Scanner input = new Scanner(System.in);
	 
	 int costOfFirst = input.nextInt();
	 int initialAmount = input.nextInt();
	 int noOfBananas = input.nextInt();
	 int totalCost=0;
	 int borrow;
	 for(int i=1;i<=noOfBananas;i++){

		  totalCost = totalCost+costOfFirst*i; 
	 }
	 if(totalCost>initialAmount){
	 borrow = totalCost - initialAmount;}
	 else{
		 borrow=0;
	 }
	 System.out.println(borrow);
 }
}
