Longest Arithmetic Subarray

Given an array of integers, your task is to determine the length of the longest contiguous subarray that forms an arithmetic progression. An arithmetic progression is a sequence where the difference between consecutive elements is constant. If the array has less than 2 elements, output 0.

Formally, for an array \(a_1, a_2, \ldots, a_n\), a contiguous subarray \(a_l, a_{l+1}, \ldots, a_r\) (with \(r-l+1 \ge 2\)) is arithmetic if there exists a constant \(d\) such that for all \(i\) with \(l+1 \le i \le r\), \(a_i - a_{i-1} = d\). Find the maximum such length in the given array.

inputFormat

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

outputFormat

Output a single integer representing the length of the longest arithmetic subarray in the given array.

7
10 7 4 6 8 10 11

4