Codeforces 546-A problem solution

A. Soldier and Bananas

time limit per test 1 second

memory limit per test 256 megabytes

input standard input

output standard output

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

Solution

• [tab]
• C++

• #include<iostream>
  using namespace std; 
  int main()
  {
      int k,n,w,sol;
      cin>>k>>n>>w;
      w=w*(w+1)/2;
      sol=k*w-n;
      if(sol<=0)
          sol=0;
          cout<<sol<<endl;
          return 0;
  }