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.io.*;
import java.util.*;
public class Main{
    public static void main(String args[]) throws IOException{
        int k,n,w,sum=0;
        BufferedReader b =new BufferedReader(new InputStreamReader(System.in));
        String A=b.readLine();
        String[] s=A.split(" ");
        k=Integer.parseInt(s[0]);
        n=Integer.parseInt(s[1]);
        w=Integer.parseInt(s[2]);
        for(int i=1;i<=w;i++){
            sum=sum+i*k;
        }
        int r;
        if(sum<=n){
            r=0;
        }
        else{
            r=sum-n;
        }
        System.out.println(r);
    }
}