Task: Sentence Ordering
Input (English): Steps: (1) The bird picks a tree (2) The bird collects twigs and other refuse (3) The bird makes sides with twigs and other things (4) The bird adds softer material to the inside (5) The nest is done.  
Where does the following step fit into the given list of steps: The bird makes a flat base with twigs 
Output (English):  After step 2.