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.lang.*;
import java.util.*;

public class Test{
    
    public static void main(String[] args){
        int first, money, count;
        Scanner sc = new Scanner(System.in);
        String[] values = sc.nextLine().split(" ");
        first = Integer.parseInt(values[0]);
        money = Integer.parseInt(values[1]);
        count = Integer.parseInt(values[2]);
        
        int sum = 0;
        for(int i=1;i<=count;i++){
            sum += i*first;
        }
        
        if(sum<money){
            System.out.println(0);
            return;
        }
        
        System.out.println(sum-money);
    }
}