diff --git a/day07/common/filesystem.go b/day07/common/filesystem.go
index 9189ed8..e61fa44 100644
--- a/day07/common/filesystem.go
+++ b/day07/common/filesystem.go
@@ -6,40 +6,45 @@ import (
 	"strings"
 )
 
+type FileBase interface {
+  GetSize() int
+  GetName() string
+}
+
 type File struct {
   name string
   size int
 }
 
-func (file File) GetSize() int {
+func (file *File) GetSize() int {
   return file.size
 }
 
-func (file File) GetName() string {
+func (file *File) GetName() string {
   return file.name
 }
 
 type Folder struct {
   name string
-  subfolders []*Folder
-  files []File
+  content []FileBase
   parent *Folder
 }
 
-func (folder Folder) GetSize() int {
+func (folder *Folder) GetSize() int {
   sum := 0
-  for _, folder := range folder.subfolders {
-    sum += folder.GetSize()
-  }
-  for _, file := range folder.files {
+  for _, file := range folder.content {
     sum += file.GetSize()
   }
   return sum
 }
 
+func (folder *Folder) GetName() string {
+  return folder.name
+}
+
 func (folder Folder) GetSubfoldersUnderSize(size int) []*Folder {
   folders := []*Folder{}
-  for _, subfolder := range folder.subfolders {
+  for _, subfolder := range folder.GetSubfolders() {
     if subfolder.GetSize() <= size {
       folders = append(folders, subfolder)
     }
@@ -50,7 +55,7 @@ func (folder Folder) GetSubfoldersUnderSize(size int) []*Folder {
 
 func (folder Folder) GetSubfoldersOverSize(size int) []*Folder {
   folders := []*Folder{}
-  for _, subfolder := range folder.subfolders {
+  for _, subfolder := range folder.GetSubfolders() {
     if subfolder.GetSize() >= size {
       folders = append(folders, subfolder)
     }
@@ -59,42 +64,50 @@ func (folder Folder) GetSubfoldersOverSize(size int) []*Folder {
   return folders
 }
 
-func (folder Folder) GetName() string {
-  return folder.name
+func (folder *Folder) GetSubfolders() []*Folder {
+  subfolders := []*Folder{}
+  for _, file := range folder.content {
+    if folder, ok := file.(*Folder); ok {
+      subfolders = append(subfolders, folder)
+    }
+  }
+  return subfolders
 }
 
-func (folder Folder) GetSubfolders() []*Folder {
-  return folder.subfolders
-}
-
-func (folder Folder) GetFilers() []File {
-  return folder.files
+func (folder *Folder) GetFiles() []*File {
+  files := []*File{}
+  for _, file := range folder.content {
+    if file, ok := file.(*File); ok {
+      files = append(files, file)
+    }
+  }
+  return files
 }
 
 func (folder *Folder) GetOrCreateFolder(name string) *Folder {
-  for _, subfolder := range folder.subfolders {
+  for _, subfolder := range folder.GetSubfolders() {
     if subfolder.GetName() == name {
       return subfolder
     }
   }
-  newFolder := Folder{name, []*Folder{}, []File{}, folder}
-  folder.subfolders = append(folder.subfolders, &newFolder)
+  newFolder := Folder{name, []FileBase{}, folder}
+  folder.content = append(folder.content, &newFolder)
   return &newFolder
 }
 
-func (folder *Folder) GetOrCreateFile(name string, size int) File {
-  for _, file := range folder.files {
+func (folder *Folder) GetOrCreateFile(name string, size int) *File {
+  for _, file := range folder.GetFiles() {
     if file.GetName() == name {
       return file
     }
   }
   newFile := File{name, size}
-  folder.files = append(folder.files, newFile)
-  return newFile
+  folder.content = append(folder.content, &newFile)
+  return &newFile
 }
 
 func Parse(scanner bufio.Scanner) Folder {
-  rootFolder := Folder{"/", []*Folder{}, []File{}, nil}
+  rootFolder := Folder{"/", []FileBase{}, nil}
   var currentFolder *Folder
 
   for scanner.Scan() {
diff --git a/day07/ex2/main.go b/day07/ex2/main.go
index cc3e057..79df0d9 100644
--- a/day07/ex2/main.go
+++ b/day07/ex2/main.go
@@ -10,7 +10,7 @@ import (
 
 func main() {
   rootFolder := common.Parse(*bufio.NewScanner(os.Stdin))
-  folders := append(rootFolder.GetSubfoldersOverSize(8381165), &rootFolder)
+  folders := append(rootFolder.GetSubfoldersOverSize(30000000 - (70000000 - rootFolder.GetSize())), &rootFolder)
   min := math.MaxInt32
 
   for _, folder := range folders {