## Algorithm

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  ≤  10000 ≤ 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
Copy
`3 17 4`
output
Copy
`13`

## Code Examples

### #1 Code Example with C++ Programming

```Code - C++ Programming```

``````#include<iostream>
using namespace std;

int main(){
int k, n, w;
cin>>k;
cin>>n;
cin>>w;

int sum = 0;
for(int i = 1; i <i= w; i++){
sum += i*k;
}
int b = (sum - n) > 0 ? (sum - n) : 0;
cout<i<ib;
return 0;

}``````
Copy The Code &

Input

cmd
3 17 4

Output

cmd
13