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 in=new Scanner(System.in);
int k=in.nextInt();
int n=in.nextInt();
int w=in.nextInt();
int sum=0;
for(int i=1;i<=w;i++)
{
int p=i*k;
sum=sum+p;
}
if(sum>n)
{
int y=sum-n;
System.out.println(y);
}
else
System.out.println("0");
}
}
