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