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.*;
public class banana {

    public static void main(String[] args) throws IOException {
        BufferedReader br =new BufferedReader(new InputStreamReader(System.in));
        String arr[]=br.readLine().split(" ");
        int cost=Integer.parseInt(arr[0]);
        int money=Integer.parseInt(arr[1]);
        int quantity=Integer.parseInt(arr[2]);
        cost=(cost*quantity*(quantity+1))/2;
        if(money>cost)
            System.out.println("0");
        else
            System.out.println(""+(cost-money));
    }
    
}
