Generate a topic word for the given sentence. A topic word is usually the name of a person, place, animal, concept or object the sentence is focusing on.

Example Input: heybeliada is an island in sea of marmara in turkey.
Example Output: heybeliada

Example Input: in 1920 the name was changed from fv to sv werder bremen.
Example Output: werder bremen

Example Input: the chronicles of narnia: prince caspian is a 2008 fantasy movie by disney and walden media.
Example Output:
the chronicles of narnia: prince caspian