Разобрать код вычисления факториала - Visual Basic .NET

Public Class Form1
    Dim k As Integer
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim res, i, kontr, f As Integer
        f = TextBox1.Text
        TextBox2.Text = 1
        res = Fact(f)
        TextBox3.Text = res
        kontr = 1
        For i = 1 To f
            kontr = kontr * i
 
        Next
        TextBox4.Text = kontr
    End Sub
    Function Fact(ByVal N As Long) As Long
        Console.WriteLine(N)
        Dim m As Integer
        If N <= 0 Then
            m = 1
        Else
            TextBox2.Text = TextBox2.Text + 1
            m = Fact(N - 1) * N
        End If
        Console.WriteLine(m)
        Return m
 
    End Function
End Class