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: the boiling point of a substance is the temperature at which the substance boils, or enters a state of rapid evaporation.
Example Output: boiling point

Example Input: rita gam (april 2, 1927march 22, 2016) was an american and television actress and documentary filmmaker.
Example Output: rita gam

Example Input: john mercer langston (december 14, 1829 – november 15, 1897) was a dean at howard university.
Example Output:
john mercer langston