Untitled

#include <iostream>
using namespace std;
int main()
{
	int n,summ = 0, j = 0;
	int a[100];
	cin >> n;
	for (int i = 0; i < n; i++)
	{
		a[i] = j;
		summ += j;
		j += 2;
	}
	cout << summ;
	
}