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 sc = new Scanner(System.in);

       int k = sc.nextInt();
       int n = sc.nextInt(); 
       int w = sc.nextInt();

       int j = k;
       int sum = 0;
       for (int i = 1; i <= w; i++) {
           sum += i * j;
       }

       if (sum > n) {
       System.out.println(Math.abs(n - sum));
       }else{
           System.out.println(0);
       }
    }
}