TASK DEFINITION: This task is about identifying the subject of a given sentence. The subject of a sentence is the person, place, or thing that is performing the action of the sentence. The subject represents what or whom the sentence is about. Each sentence in this task is guaranteed to contain a single subject. The input is a sentence and the output is the identified subject of that sentence.
PROBLEM: A Wizard of Mars is preceded by Wizards at War.

SOLUTION: A Wizard of Mars

PROBLEM: Sweden won 2 medals in total

SOLUTION: Sweden

PROBLEM: The leader of the United States was Barack Obama.

SOLUTION:
United States