Level Order Traversal

Given a binary tree in level-order form, print its nodes level by level from top to bottom, one level per line.

Input Format

The first line contains an integer M, the number of level-order tokens. The second line contains M space-separated tokens (integers or null). It is blank when M is 0.

Output Format

For each level from the root downward, print the values on that level separated by single spaces, one level per line. Print nothing for an empty tree.