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 prac4{ 
public static void main(String ... args){ 
Scanner in=new Scanner(System.in); 
long k=in.nextLong(); 
long n=in.nextLong(); 
long w=in.nextLong(); 
long need=w*(w+1)*k/2; 
System.out.println(need>=n?need-n:0); 
} 
}
 		   	 	 		      		  	 		  		