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.*;
public class SodiersAndBananas {
 
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
          int k = sc.nextInt();
          int n = sc.nextInt(); 
          int w = sc.nextInt();
          int sum =0;
          for(int i=1 ;i<=w;i++){
			  sum += i*k; 
		  }
		  if(sum <= n)
		  System.out.println(0);
		  else 
		   System.out.println(sum-n);
     }
}


