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 senators mentioned the doctor behind the lawyers .
The doctor mentioned the lawyers .

The presidents next to the scientists saw the students .
The scientists saw the presidents .

The secretary called the president next to the doctor .

The doctor called the secretary .