I've read all posts but still do not understand what's wrong.
my solution:
-ignores names mentioned twice
-output 2 spaces, but not points
-outputs only 20 first names
-consists of 'sun' in the beginning

can anyone please give any tests or hints?

Edited by author 08.10.2012 08:31

Edited by author 08.10.2012 08:31

try
+sun1
+sun2
+sun3
...
+sun20
?sun

Answer:
sun
sun1
....
sun19

Or change 20 to 3 for testing.

Deleted, my mistake

Edited by author 22.06.2014 14:36

try
+sun1
+sun2
+sun3
...
+sun20
?sun

Answer:
sun
sun1
....
sun19


this is not right..
I got AC using Trei and the correct answer is
sun
  sun1
  sun10
  sun11
  ...
  sun9