阶乘

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace jiecheng
{
    class Program
    {
        static void Main(string[] args)
        {
             int i, n;    
            double sum = 1;    
            Console.WriteLine("请输入n的值：");  
            n = int.Parse(Console.ReadLine());  
            for (i = 1; i <= n; i++)          
                sum *= i;         
            Console.WriteLine("n!={0}", sum); 
        }
    }
}