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 A546
{
  public static void main(String[] args)
  {
    Scanner in=new Scanner(System.in);
    int[] a= new int[3];
for(int i = 0; i < 3; i++)
{
    a[i] = in.nextInt();
}
    int b=0;
    for (int i=1; i<=a[2]; i++)
    {
      b=b+i*a[0];
    }
    if (b<=a[1])
    {
      System.out.println("0");
    }
    else
    {
      int c=b-a[1];
      System.out.println(c);
    }
  }}
      