Module Module1

    Sub Main()

        Dim tmp As String() = Split(Console.ReadLine())

        Dim A As Integer = CInt(tmp(0))
        Dim B As Integer = CInt(tmp(1))

        Dim w = A - B * 2

        Console.WriteLine(If(w > 0, w, 0))
        'Console.Read()

    End Sub

End Module
