Module Module1

    Function log10(ByVal x As Double)
        log10 = Math.Log(x) / Math.Log(10)
        Return log10
    End Function

    Sub Main()

        Dim cislo, y As Double

        Console.Write("Zadejte cislo: ")
        cislo = Console.ReadLine

        y = log10(cislo)

        Console.WriteLine("log({0})={1}", cislo, y)

        Console.ReadLine()

    End Sub

End Module