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 n, m;
int main() {
  int i, j, T;
  long long k, total, w;
  while (scanf("%I64d%I64d%I64d", &k, &total, &w) != EOF) {
    long long ans = (1 + w) * w / 2;
    ans *= k;
    if (ans - total >= 0)
      printf("%I64d\n", ans - total);
    else
      printf("0\n");
  }
  return 0;
}
