An excavation log records a binary tree of soil samples. Analysts want the readings listed starting from the deepest level and working up to the surface (the root). Emit the node values level by level from the deepest level to the shallowest; within each level, keep the natural left-to-right order.
Input format
Line 1: an integer n, the number of tokens on the next line.
Line 2: n space-separated tokens describing a binary tree in level-order (breadth-first). The first token is the root's value. Reading left to right, keep a queue of already-created nodes; for each node taken from the front of the queue, the next two tokens are its left child then its right child, where the token null marks a missing child. Only non-null children are added to the queue. Trailing null tokens for absent children at the deepest level may be omitted. Every node value is an integer.
Output format
A single line: all node values ordered from the deepest level up to the root, left-to-right within each level, space-separated.
Constraints
- 1 <= n <= 129
- The tree has at least 1 and at most 40 nodes.
- Each node value is an integer with -1000 <= value <= 1000.