Imports System.Collections.Generic
Imports System.Console

Module Program
    Sub Main()
        Dim N As Integer = CInt(NextString())
        Dim s As String = NextString()
        Dim t As String = NextString()

        Dim overlap As Integer = 0
        For i As Integer = 1 To N
            If Right(s, i) = Left(t, i) Then
                overlap = i
            End If
        Next

        WriteLine(2 * N - overlap)
    End Sub

    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
