Introduction to Doubly Linked List

Introduction to Doubly Linked List

Implement a doubly linked list supporting insertion and deletion from both ends.

Input format

The first line contains N. The second line contains the N node values in order.

Output format

Build a doubly linked list from the values. Print two lines: the list traversed forward, then traversed backward.

Constraints

• Values fit in a 64-bit signed integer
• Trailing whitespace and a trailing newline are ignored by the judge

Read from stdin, write to stdout. Sample cases below show the exact format.

4
1 2 3 4

1 2 3 4
4 3 2 1

1
7

7
7