TASK DEFINITION: In this task, you are given a premise sentence. Your task is to write a new sentence by substituting the subject and object (i.e., the input's subject should be output's object and vice versa.). The generated sentence must be fluent and shouldn't change the voice (i.e., passive or active) of the input.
PROBLEM: The president who the doctor recommended introduced the tourist .

SOLUTION: The doctor introduced the president .

PROBLEM: The tourist in front of the professors introduced the athletes .

SOLUTION: The athletes introduced the tourist .

PROBLEM: The professor stopped the author .

SOLUTION:
The author stopped the professor .