using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApp1
{
class F
{
int invalue = 10;
public static int Sum(int invalue)
{
if (invalue <= 2)
return invalue;
else
return invalue * Sum(invalue - 2);
}
}
class Program
{
static void Main(string[] args)
{
Console.WriteLine("F.Sum");