SoldiersandBananas.cpp

// A. Soldier and Bananas
// time limit per test1 second
// memory limit per test256 megabytes
// inputstandard input
// outputstandard 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
// inputCopy
// 3 17 4
// outputCopy
// 13

#include<bits/stdc++.h>
#define TestCase int t; cin>>t; while(t--)
using namespace std;

int sol(int& totalAmountRaise, int& n){

    if(totalAmountRaise<=n){
        return 0;
    }
    totalAmountRaise = totalAmountRaise-n;
    return totalAmountRaise;
}
int main(){
 
   int k,n,w;
   cin>>k>>n>>w;

   int totalamountRaise =0;
   for(int i=1;i<=w;i++){
      
      totalamountRaise+=k*i;
     

   }


    cout<<sol(totalamountRaise,n);




}