N阶乘

class Program
    {
        public static int Fac(int n)
        {
            int Fac = 1;
            for (; n > 0; n--)
            {
                Fac = Fac * n;
            }
            return Fac;
        }

        static void Main(string[] args)
        {
            Console.WriteLine("请输入N的值");
            int n = int.Parse(Console.ReadLine());
            Console.WriteLine("{0}的阶乘为{1}", n, Fac(n));
            Console.ReadLine();
        }