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.lang.Math;
public class Main{
    public static void main(String args[])
    {
        Scanner sc = new Scanner(System.in);
        int cost = sc.nextInt();
        int doll = sc.nextInt();
        int num = sc.nextInt();
        int sum=0;
        
        for(int i=1;i<=num;i++)
            sum = sum + (cost*i);
        
        if(sum>doll)
        System.out.println(sum-doll);
        else
        System.out.println("0");

  }
}