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 x
{
    public static void main(String args[])
    {
        Scanner sc = new Scanner(System.in);
        
        int k[] = new int[1000+1];
        k[0]  = sc.nextInt();
        long n = sc.nextLong();
        int w = sc.nextInt();
        int sum = 0;
        long ans = 0;
    
        for(int i=1;i<=w;i++)
        {
            k[i] = k[0]*i;
        }
        
        for(int i=1;i<=w;i++)
        {
            sum = sum + k[i];
        }
        
        ans = sum-n;
        
        if(n>sum)
        {
            System.out.println(0);
        }
        else
        {
        System.out.println(ans);
        }
        
    }
}

