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 S {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        String s = in.nextLine();

       String arr[] = s.split(" ");

       int k = Integer.parseInt(arr[0]);
       int n = Integer.parseInt(arr[1]);
       int w = Integer.parseInt(arr[2]);
       int sum=0;
       for(int i=1;i<=w;i++){
           sum = sum + (i*k);
       }
       if((sum-n)>0) {
           System.out.println(sum - n);
       }
       else {
           System.out.println("0");
       }
    }


}
