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 SolidersAndBananas {
  public static void main (String[] args) {
    Scanner s = new Scanner(System.in);
    
    int c = s.nextInt();
    int n = s.nextInt();
    int w = s.nextInt();
    
    int total = 0;
    for (int i = 0; i < w; i++) {
      total += (i + 1) * c;
      // System.out.println("Banana " + (i + 1) + ": " + total);
    }
    
    if (total > n) {
      System.out.println(Math.abs(total - n));
    } else {
      System.out.println(0);
    }
    
  }
}