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