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
//package solider;

import java.util.Scanner;

public class SOLIDER {

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