Print numbers in increasing and decreasing order in same function.

Difficulty: Hard

Phase: 3 · Recursion

XP Reward: 30 XP

Topics: Recursion, Hard

Supported Languages: Python, JavaScript, C, C++, Java

Problem Description

Given N, print numbers from 1 to N and then back down to 1 in a single recursive traversal. Input Format: Read input from standard input (stdin). Output Format: Print the result to standard output (stdout).

Constraints

-10^9 <= N <= 10^9

Examples

Example 1

Input: 3

Output: 1 2 3 2 1

Explanation: Sample execution for input 3