Module Module1

    Sub Main()

        Dim N As Integer = Console.ReadLine()
        Dim A As New List(Of Integer)
        Dim C As New List(Of Integer)(Console.ReadLine().Split().Select(Function(s) CInt(s)))
        Dim i As Integer

        C.Insert(0, C(0))
        C.Add(C(C.Count - 1))

        For i = 0 To C.Count - 2
            A.Add(Math.Min(C(i), C(i + 1)))
        Next

        Console.WriteLine(A.Sum)

        'Console.ReadLine()

    End Sub

End Module
