using System;

public class Program

{

    private static int GetSumOfN(int n)

    {

        return n * (n + 1) / 2;

    }

​

    private static int CountOfTriangles(int n)

    {

        if (n < 1)

        {

            throw new ArgumentException("N should be greater than 0");

        }

        if (n == 1)

        {

            return 1;

        }

​

        int[] sumUp = new int[n + 1];

        int[] sumDown = new int[n + 1];

        sumUp[1] = 1;   sumUp[2] = 3;

        sumDown[1] = 0; sumDown[2] = 1;

        for (int i = 2; i <= n; i++)

        {

            sumUp[i] = sumUp[i - 1] + GetSumOfN(i);

            sumDown[i] = sumDown[i - 2] + GetSumOfN(i - 1);

        }

        return sumUp[n] + sumDown[n];

    }   

    public static void Main()

    {

        Console.WriteLine("UniLecs");

        Console.WriteLine(string.Format("Answer({0})= {1}", 1, CountOfTriangles(1))); // 1

        Console.WriteLine(string.Format("Answer({0})= {1}", 2, CountOfTriangles(2))); // 5

        Console.WriteLine(string.Format("Answer({0})= {1}", 3, CountOfTriangles(3))); // 13

        Console.WriteLine(string.Format("Answer({0})= {1}", 4, CountOfTriangles(4))); // 27

        Console.WriteLine(string.Format("Answer({0})= {1}", 5, CountOfTriangles(5))); // 48

        Console.WriteLine(string.Format("Answer({0})= {1}", 6, CountOfTriangles(6))); // 78

    }

}