Given a list of steps and an additional step, determine where the step fits into the original list of steps. A correct answer, correctly places the given step into the set of steps so that it creates a new plausible set of steps. Output must be formatted as 'After step n', where n is the step number after which the given additional step is to be inserted.

Steps: (1) Enters the lungs (2) The oxygen fills the sacs in your lungs (3) Carbon dioxide is removed from the lungs and exhaled (4) The oxygen is pass throughout your body.  
Where does the following step fit into the given list of steps: Air is taken through the mouth 
 Before step 1. 