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 JavaApplication1 {

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