A soldier wants to buy *w* bananas in the shop. He has to pay *k* dollars for the first banana, 2*k* 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?
The first line contains three positive integers *k*, *n*, *w* (1  ≤  *k*, *w*  ≤  1000, 0 ≤ *n* ≤ 10<sup class="upper-index">9</sup>), the cost of the first banana, initial number of dollars the soldier has and number of bananas he wants.
import java.util.*;

public class BananaCostCalculator {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int costPerBanana = scanner.nextInt();
        int totalBudget = scanner.nextInt();
        int numWeeks = scanner.nextInt();
        int totalCost = 0;

        for (int week = 1; week <= numWeeks; week++) {
            int weeklyCost = week * costPerBanana;
            totalCost += weeklyCost;
        }

        if (totalCost <= totalBudget) {
            System.out.println(0);
            System.exit(0);
        }

        System.out.println(totalCost - totalBudget);
    }
}
