Public Class Form1
    Private Sub IntegerTest_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
        If Int(TextBox1.Text) > UShort.MaxValue Then
            MsgBox("數字會不會太大了?? X<", 48, "Error")
            Return
        End If

        Dim fact As UShort = CUShort(TextBox1.Text)
        Dim ans As New List(Of ULong) From {1}
        Label1.Text = "運算中..."
        Me.Cursor = Cursors.WaitCursor
        Application.DoEvents() 'Display

        Dim nw As Date = Now

        'Start Calculating
        For i As UShort = 2 To fact
            For j As Long = ans.Count - 1 To 0 Step -1
                Dim nwans As ULong = ans(j) * i
                If nwans > 99999999999999 Then
                    If j < ans.Count - 1 Then
                        ans(j + 1) += (Int(nwans / 100000000000000))
                    Else
                        ans.Add(Int(nwans / 100000000000000))
                    End If
                    ans(j) = Strings.Right(nwans, 14)
                Else
                    ans(j) = nwans
                End If
            Next
        Next

        Dim fnans As String = ""
        For Each a As ULong In ans
            fnans = a.ToString("00000000000000") & fnans
        Next

        TextBox2.Text = fnans

        Label1.Text = "Time Used: " & (Now - nw).ToString()
        Me.Cursor = Cursors.Default
    End Sub
End Class