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 Solution{
    public static void main(String args[]){
        Scanner sc = new Scanner(System.in);
        int k = sc.nextInt(); //cost of 1st banana, 2nd banana 2k
        int n = sc.nextInt(); // initial dollars
        int w = sc.nextInt(); // no of bananas
        
        int cost = k*((w*(w+1))/2);
        if(cost < n)
            System.out.println("0");
        else
            System.out.println(cost - n);
    }
}