Imports System.Collections.Generic
Imports System.Console

Module Program
    Sub Main()
        Dim n As Integer = NextInt()
        Dim a(3 * n - 1) As Integer
        For i As Integer = 0 To 3 * n - 1
            a(i) = NextInt()
        Next
        Array.Sort(a)
        Array.Reverse(a)

        Dim ans As Long = 0
        For i As Integer = 0 To n - 1
            ans += a(2 * i + 1)
        Next

        WriteLine(ans)
    End Sub

    Function NextInt() As Integer
        Return CInt(NextString())
    End Function

    Function NextString() As String
        Dim result As New List(Of Char)
        Do
            Dim tmp As Integer = Read()
            If tmp < 0 Then Exit Do
            Dim nextChar As Char = Chr(tmp)

            If Not Char.IsWhiteSpace(nextChar) Then
                result.Add(nextChar)
            ElseIf nextChar <> vbCr Then
                Exit Do
            End If
        Loop
        Return New String(result.ToArray())
    End Function
End Module
