Imports System.Collections.Generic
Imports System.Console

Module Program
    Sub Main()
        Dim N As Integer = NextInt()
        Dim L As Integer() = New Integer(2 * N - 1) {}
        For i As Integer = 0 To 2 * N - 1
            L(i) = NextInt()
        Next
        Array.Sort(L)

        Dim ans As Integer
        For i As Integer = 0 To N - 1
            ans += L(2 * i)
        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
