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 Solution{
       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 = k;
             for(int i=2;i<=w;i++)
             {
                    sum = sum + i*k;
             }
             if(sum > n)
             {
                 System.out.print(sum - n);
             }
             else
             {
                 System.out.print(0);   
             }
             
       }
}