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
#include <bits/stdc++.h>
int main() {
  int per_banana, total_dollar, total_banana;
  scanf("%d %d %d", &per_banana, &total_dollar, &total_banana);
  int total_cost = 0;
  int i;
  for (i = 1; i <= total_banana; i++) {
    total_cost += i * per_banana;
  }
  if (total_cost > total_dollar) {
    printf("%d\n", total_cost - total_dollar);
  } else
    printf("0\n");
  return 0;
}
