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