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 Main
{
	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		String[] initialArr = scanner.nextLine().split(" ");
		int costBase = Integer.parseInt(initialArr[0]);
		int moneySoldier = Integer.parseInt(initialArr[1]);
		int bananaCount = Integer.parseInt(initialArr[2]);
		
	    int totalCost = costBase * ((bananaCount*(bananaCount+1))/2);
	    int dif = totalCost - moneySoldier;
	    
	    if (dif > -1){
	        System.out.println(dif);
	    } else{
	        System.out.println(0);
	    }
    }
}
