Given a Binary Tree of size N, find all the nodes which don't have any sibling. Root node can not have a sibling.

Example 1:

Input :
       37
      /   
    20
    /     
  113 

Output: 20 113
Explanation: 20 and 113 dont have any siblings.

Example 2:

Input :
       1
      / \
     2   3 

Output: -1
Explanation: Every node has a sibling.

Your Task:  
You dont need to read input or print anything. Complete the function noSibling() which takes the root of the tree as input parameter and returns a list of integers containing all the nodes that don't have a sibling in sorted order. If all nodes have a sibling, then the returning list should contain only one element -1.

Expected Time Complexity: O(N)
Expected Auxiliary Space: O(Height of the tree)

Constraints:
1 ≤ N ≤ 10^4
All nodes have distinct values.