codeforces 546A Soldier and Bananas

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 payk dollars for the first banana, 2k dollars for the second one and so on (in other words, he has to payi·k dollars for the i-th banana).

He has n dollars. How many dollars does he have to borrow from his friend soldier to buyw 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, output0.

Examples

Input

3 17 4

Output

13

AC:

#include<bits/stdc++.h>
using namespace std;
int main()
{
    int k,n,w;
    scanf("%d%d%d",&k,&n,&w);
    int sum=0;
    for(int i=1;i<=w;i++)
        sum+=i*k;
    if(n<sum)
        printf("%d\n",sum-n);
    else
        printf("0\n");
}