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.io.*;
import java.util.*;

public class A
{
   public static void main(String[] args)
   {
      Scanner s = new Scanner(System.in);
      int k = s.nextInt();
      int n=s.nextInt();
      int w=s.nextInt();
      
      int ans = 0;
      for(int i = 1; i <= w; ++ i)
      {
          n -= k*i;
      }
      
      if(n<0)
        System.out.print(n*(-1));
      else
        System.out.print(0);
    }
}