Task: Sentence Ordering
Input (English): Steps: (1) A larva is born (2) The caterpillar eats constantly until it grows bigger (3) The caterpillar starts to form a cocoon around itself (4) After some time the cocoon hatches (5) And a butterfly is born.  
Where does the following step fit into the given list of steps: The caterpillar becomes a pupa 
Output (English):  After step 3.