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() {
  long long k, n, w;
  long long total = 0;
  std::cin >> k >> n >> w;
  if ((1 <= k) && (w <= 1000) && (0 <= n) && (n <= 1000000000)) {
    for (int i = 0; i <= w; i++) {
      total = total + k * i;
    }
    if (0 <= (total - n)) {
      std::cout << total - n;
    } else {
      std::cout << "0";
    }
  } else {
    std::cout << " ";
  }
}
