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.Scanner;
import java.io.*;
import java.math.*;
public class aa1 {
	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++) {
			sum+=i*(k);
			
			
			
		}
	
		int s2=sum-n;
		if(s2<=0) {
			System.out.print("0");
		}
		else {
			System.out.print(s2);
		}

	}
		
		
		
		
		
		
		
		
		
	
}
