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 author stopped the secretaries .
The secretaries stopped the author .

The doctors near the secretary contacted the lawyer .
The lawyer contacted the doctors .

The artist mentioned the president next to the professor .

The president mentioned the professor .