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.*;
import java.lang.*;
public class Soldier
{
    static public void main(String[] args)
    {
        int n,w,k,b=0,i;
        Scanner s= new Scanner(System.in);
        k=s.nextInt();
        n=s.nextInt();
        w=s.nextInt();
        for(i=1;i<=w;i++)
            b+=i;
        if(k*b-n>0)
            System.out.print(k*b-n);
        else System.out.print(0);

    }
}
