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.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.stream.Stream;

public class SoliderAndBananas {
    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        int[] inputs = Stream.of(reader.readLine().trim().split("\\s+")).mapToInt(Integer::parseInt).toArray();
        int money = moneyToBorrow(inputs);
        System.out.println(Math.max(money, 0));
    }

    private static int moneyToBorrow(int[] inputs) {
        return inputs[0]*(inputs[2] * (inputs[2]+1))/2 - inputs[1];
    }
}
