Longest Contiguous Arithmetic Subarray

Given an array of integers, your task is to find the longest contiguous subarray that forms an arithmetic sequence. An arithmetic sequence is a sequence of numbers where the difference between consecutive elements is constant. Formally, a sequence \( a, a+d, a+2d, \dots \) is arithmetic, where \( d \) is the common difference.

If there are multiple subarrays with the maximum length, return the first one encountered. If the length of the array is less than 2 or no arithmetic subarray can be found, output an empty result.

Note: The input is read from standard input and the result must be printed to standard output.

inputFormat

The first line of input contains a single integer \( n \) representing the number of elements in the array. The second line contains \( n \) space-separated integers.

outputFormat

Output the elements of the longest contiguous arithmetic subarray in order, separated by a single space. If there is no valid arithmetic subarray (i.e. when \( n < 2 \)), output an empty line.

9
1 3 5 7 9 10 20 30 40

1 3 5 7 9