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 doctor contacted the judges .
The judges contacted the doctor .

The tourists in front of the senator thanked the student .
The student thanked the senator .

The president behind the doctors called the secretary .

The secretary called the president .