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: "polythene pam" is a song written by john lennon, credited to lennon/mccartney, and performed by the beatles on their album "abbey road".
Example Output: polythene pam

Example Input: skagit valley is a valley in washington in the united states.
Example Output: skagit valley

Example Input: habib thiam (21 january 1933 – 26 june 2017) was a senegalese politician.
Example Output:
habib thiam