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 in = new Scanner(System.in);
        
        int k = Integer.parseInt(in.next());
        long n = Integer.parseInt(in.next());
        int w = Integer.parseInt(in.next());
        int re=0;
        
        for(int i=1;i<w+1;i++){
            int a = i*k;
            re=re+a;
        }
        int result= (int) (re-n);
        if(result>=0)System.out.println(result);
        else System.out.println(0);
    }
}