1 0 a
   2 1 b
   3 2 c
   4 3 hello
   5 4 world
   6 a
   7 b
   8 c
   9 hello
  10 world
  11 3 hello
  12 4 world
  13 hello
  14 world
  15 3 hello
  16 4 world
  17 hello
  18 world
  19 3 hello
  20 4 world
  21 hello
  22 world