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.

Ex Input:
the world conference of life and work was an ecumenic conference.

Ex Output:
world conference of life and work

Ex Input:
dennis kearney (18471907) was an american politician who was himself an immigrant from ireland.

Ex Output:
dennis kearney

Ex Input:
the hydrogenophilaceae are a family of betaproteobacteria, with two genera.

Ex Output:
hydrogenophilaceae