static void Main(string [] args)
{
NumberManipulator n = new NumberManipulator();
Console.WriteLine("6 的阶乘是: {0}", n.factorail(6));
Console.WriteLine("7 的阶乘是: {0}", n.factorail(7));
Console.WriteLine("8 的阶乘是: {0}", n.factorail(8));
}
