Factorial (.net)

        Using System;
namespace Factorial
{
    class prg
    {
      static void main(string [] args)
    {
      console.writeline("Enter a number");
      int F=Int32.Parse(console.Readline(1));
      for(int i=1; i<F; i++)
      {
         fr=fr+i;
      }
      console.writeline("{0}i{i}",F,fr);
      console.writeline("Factorial number",fr);
      }
   }
}