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.*;

public class SoldierandBananas {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		
		Scanner scn = new Scanner(System.in);
		int k = scn.nextInt() ;
		int n = scn.nextInt();
		int w = scn.nextInt() ; 
		
		int sum = (w * (w+1))/2 ; 
		int ar = sum * k ;
		int borrow = ar - n  < 0 ? 0 : ar-n;
		
		System.out.println(borrow);
		
		

	}

}
