LogiQuest

378. Level Order by Lines

EasyBFS

Print the tree level by level, one line per level.

Input format

Line 1: n (number of level-order entries) Line 2: the values in level order, -1 for a missing child

Output format

One line per level.

Example 1

Input

7
3 9 20 -1 -1 15 7

Output

3
9 20
15 7

Example 2

Input

1
1

Output

1

Constraints

1 ≤ nodes ≤ 10⁴

Read input from standard input and print the answer to standard output. Your code is judged against 5 test cases, most of them hidden.

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