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.StringTokenizer;
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 x=Integer.parseInt(st.nextToken());
		int y=Integer.parseInt(st.nextToken());
		int z=Integer.parseInt(st.nextToken());
		int sum=0;
		for(int i=1;i<=z;i++){
			sum+=x*i;
		}
		if(sum-y<0)
		System.out.print(0);
		else
		System.out.print(sum-y);
	}
}