1  a
 2  b
 3  c
 4  c/a
 5  c/b
 6  b/a
 7  c/b/a
 8  c//a
 9  c//b
10  b//a
11  c//b//a
12  c/b//a
13  c//b/a
14  /a
15  /b
16  /c
17  /c/a
18  /c/b
19  /b/a
20  /c/b/a
21  /c//a
22  /c//b
23  /b//a
24  /c//b//a
25  /c/b//a
26  /c//b/a
27