Coderforces Soldier and Bananas

http://codeforces.com/problemset/problem/546/A

import java.util.Scanner;

public class Soldier_and_Bananas {

public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int k = scanner.nextInt();
int n = scanner.nextInt();
int w = scanner.nextInt();
int sum = 0;
for(int i = 1; i <= w; i++) {
sum += k*i;
}
int temp = sum - n;
if(temp > 0) System.out.println(temp);
else System.out.println(0);
}
}