Instructions: 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.
Input: Steps: (1) A virus enters a host body (2) The virus enters the cell (3) The virus uses the cell like a factory to make new copies of the virus (4) The new copies of the virus leave the cell (5) Infect other cells (6) The host gets sick as its cells are damaged.  
Where does the following step fit into the given list of steps: The virus has receptors that lock onto a target cell 
Output:
 After step 1. 