Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim a, b, sayi, deger As Integer
        If Val(TextBox2.Text) <> 1 Then
            sayi = Val(TextBox2.Text)
            a = 1
            b = 2
            For z = 1 To sayi - 2
                deger = b
                b = a + b
                a = deger
            Next z
        End If
        TextBox1.Text = a
    End Sub
End Class