ACM competition, acm

ACM competition, acm

Description

A soldier wants to buyWBananas in the shop. He has to payKDollars for the first banana, 2KDollars for the second one and so on (in other words, he has to payI·KDollars forI-Th banana ).

He hasNDollars. How does dollars does he have to borrow from his friend soldier to buyWBananas?

Input

The first line contains three positive integersK, Bytes,N, Bytes,W(1 hour ≤ hourK, Bytes,W  ≤    1000, 0   ≤NLimit ≤ limit 10^{9), 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.

Sample Input

Input

3 17 4

Output

13
Question Analysis:This question is mainly about the accumulation of data. In this question, it can also be said that the accumulation of class.
Code:

#include <cstdio>#include <iostream>using namespace std;int main(){int k,n,w,sum=0;cin>>k>>n>>w;for(int i=1;i<=w;i++)sum+=i*k;if((sum-n)<0)cout<<0;else cout<<sum-n;return 0;}