Given an unordered list of pairs where each pair represents a parent-child relationship (not nessesary direct) in an N-ary tree. Reconstruct and return the original tree. You can assume that each node has a unique value.

Example 1:

Input: [[1, 2], [1, 3], [1, 4], [2, 4]]
Output:
     1
    / \
   2   3
  /
 4

Example 2:

Input: [[1, 2], [1, 3], [1, 4], [1, 5], [1, 6], [1, 7], [2, 4], [2, 5], [2, 7], [3, 6], [4, 7]]
Output: 
      1
     / \
    2   3
   / \   \
  4   5   6
 /
7