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: in egyptain mythology sopdet was the goddess of the star sothis.

Output: sopdet


Input: Consider Input: in greek mythology, the nereids ( "nereides") are sea nymphs, the fifty daughters of nereus, the old man of the sea, and the okeanid doris.

Output: nereid


Input: Consider Input: mafic is an adjective describing a silicate mineral or igneous rock which is rich in magnesium and iron.


Output: mafic