Task: Sentence Ordering
Input (English): Steps: (1) The oxygen travels to the lungs through the windpipe (2) The air sacs in the lungs send the oxygen into the blood stream (3) The carbon dioxide in the blood stream is transferred to the air sacs (4) The lungs expel through the nose or mouth back into the environment.  
Where does the following step fit into the given list of steps: You breathe oxygen into your body through the nose or mouth 
Output (English):  Before step 1.