VB.NET2010 给定求组合数公式为Cmn=m!/n!(m-n)!，编一程序，输入m和n的值，求Cmn的值。要用Sub过程

Module Module1Private Sub fac(ByVal x As ULong, ByRef y As ULong)Dim i&, a&a = 1For i = 1 To xa = a * iNext iy = aEnd SubSub Main()Dim m&, n&, Cmn&, c1&, c2&, c3&Console.WriteLine("m=")m = Val(Console.ReadLine())Console.WriteLine("n=")