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{
    Scanner sc = new Scanner(System.in);
    int k = sc.nextInt();
    int n = sc.nextInt();
    int w = sc.nextInt();
    int cost = 0;
    int ans = 0;
    for(int i = 1; i<w+1; i++){
      cost += k*i;
    }
    if(cost<=n){
      System.out.print(0);
    }else{
      ans = cost-n;
      System.out.print(ans);
    }
    sc.close();
  }
}