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 SoldierAndBananas {

    private static final Scanner scanner = new Scanner(System.in);
    private static int costFirstBanana;
    private static int numberOfDollars;
    private static int numberOfBananasWanted;

    public static void main(String[] args) {
        readInput();
        System.out.println(amountToBorrow());
    }

    private static void readInput() {
        costFirstBanana = scanner.nextInt();
        numberOfDollars = scanner.nextInt();
        numberOfBananasWanted = scanner.nextInt();
    }

    private static int amountToBorrow(){

        int totalCost = 0;

        for (int i = 1; i <= numberOfBananasWanted; i++) {
            totalCost += (i * costFirstBanana);
        }

        return totalCost < numberOfDollars ? 0 : (totalCost - numberOfDollars);
    }


}
