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 SoldiersAndBananas {
    //546A Soldiers and Bananas
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        
        int k = Integer.parseInt(scanner.next()); //cost of first banana
        int w = Integer.parseInt(scanner.next()); //intial amount of money
        int n = Integer.parseInt(scanner.next()); //how many bananas he wants
        int total = 0;

        for(int i = 1; i<=n;i++){
            total += i*k;
        }

        if(w>=total){
            System.out.println(0);
        }
        else{
            System.out.println(total-w);
        }

        scanner.close();
    }
}
