give root binary tree return number node value node equal average value subtreeNoteThe average n element sum n element divide n round near integerA subtree root tree consist root descendant Example 1input root 48501null6output 5explanation for node value 4 the average subtree 4 8 5 0 1 6 6 24 6 4for node value 5 the average subtree 5 6 2 11 2 5for node value 0 the average subtree 0 1 0for node value 1 the average subtree 1 1 1for node value 6 the average subtree 6 1 6example 2input root 1output 1explanation for node value 1 the average subtree 1 1 1 ConstraintsThe number nod tree range 1 10000 Nodeval 1000