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.

The senator called the athlete .
The athlete called the senator .

The president thanked the lawyer .
The lawyer thanked the president .

The author who mentioned the students introduced the lawyer .

The students introduced the author .