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 w = 0, k = 0, n = 0, i = 0, s = 0;
  while (w < 1 || k < 1 || k > 1000 || w > 1000 || n < 0 || n > 1000000000) {
    scanf("%d", &k);
    scanf("%d", &n);
    scanf("%d", &w);
  }
  for (i = 1; i < (w + 1); i++) s += i * k;
  if (n > s)
    printf("%d", 0);
  else
    printf("%d", s - n);
  return 0;
}
