Longest Contiguous Arithmetic Subarray

Given an array of N integers, your task is to find the length of the longest contiguous arithmetic subarray.

An arithmetic subarray is a subarray where the difference between consecutive elements is constant. For example, the array [10, 7, 4, 6, 8, 10, 11] has an arithmetic subarray [4, 6, 8, 10] of length 4.

Mathematically, a subarray A[i], A[i+1], ..., A[j] is arithmetic if \[ A[k+1]-A[k] = d, \quad \text{for all } i \leq k < j \] for some constant difference \(d\). If the array contains fewer than 2 elements, define the longest arithmetic subarray length to be 0.

inputFormat

The first line contains an integer N (the number of elements in the array).

The second line contains N space-separated integers representing the elements of the array.

outputFormat

Output a single integer, the length of the longest contiguous arithmetic subarray.

## sample

7
10 7 4 6 8 10 11

4

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