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.

Input: Consider Input: plankton are drifting organisms that live in the surface layers of the ocean.

Output: plankton


Input: Consider Input: language death is when a language stops being used as a first language (also called mother language or native language) and as a second language, which it then becomes an extinct language.

Output: language death


Input: Consider Input: the heat is a 2013 police comedy which stars sandra bullock and melissa mccarthy.


Output: the heat