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.Scanner;

public class soldierandbananas {
    public static void main(String[] args) {
            String[] n;
            int[]m = new int[3];
            int result = 0;
        Scanner scan = new Scanner(System.in);
        n = scan.nextLine().split(" ");
        for(int i= 0; i<3; i++){
            m[i] = Integer.parseInt(n[i]);
        }
        for(int i=1; i<=m[2]; i++){
            result += i*m[0];
        }
        if(result - m[1] <= 0){
            System.out.println(0);
        }
        else{
            System.out.println(result - m[1]);
        }
        scan.close();
    }
        
        
    }

