Task: Sentence Ordering
Input (English): Steps: (1) Water is transported to the leaves in the xylem (2) Energy harvested through light reaction is stored by forming ATP (3) Carbon dioxide and energy from ATP are used to create sugar (4) Oxygen exits the leaves through the stomata by diffusion (5) The plant reuses the water or the water exits through the stomata as water vapor.  
Where does the following step fit into the given list of steps: Carbon dioxide enters the leaves through the stomates by diffusion 
Output (English):  Before step 1.