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 arg[]){
Scanner input = new Scanner(System.in);
int k =input.nextInt(),n=input.nextInt(),w=input.nextInt(), sum=0;
     	for(int i = 1; i <= w; i++)
        {sum=sum+(i*k);}
                if (n-sum >=0)
             System.out.println(0);
                else                
       System.out.println(sum-n);

	}

}