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.*;
import java.io.*;
public class A546 {
	public static void main (String[]args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st = new StringTokenizer(br.readLine());
		int cost = Integer.parseInt(st.nextToken()); int totalCost = 0;
		int dollars = Integer.parseInt(st.nextToken());
		int needed = Integer.parseInt(st.nextToken());
		for(int i = 1; i<=needed; i++)
			totalCost += i*cost;
		System.out.print(((totalCost-dollars)>0)?totalCost-dollars:0);
	}
}