.
|-- dir1
| |-- a
| | |-- file1.txt
| | `-- file2.txt
| |-- b
| | `-- file3.txt
| `-- c
| `-- file4.txt
`-- dir2
|-- a
| |-- file5.txt
| `-- file6.txt
|-- b
| |-- file7.txt
| `-- file8.txt
`-- c
|-- file10.txt
`-- file9.txt
merged/
|-- a
| |-- file1.txt
| |-- file2.txt
| |-- file5.txt
| `-- file6.txt
|-- b
| |-- file3.txt
| |-- file7.txt
| `-- file8.txt
`-- c
|-- file10.txt
|-- file4.txt
`-- file9.txt