Longest Consecutive Sequence

You are given an unsorted array of n integers. Your task is to find the length of the longest consecutive elements sequence.

Consecutive elements are numbers that appear in a sequence where each number is exactly 1 greater than the previous number. For example, in the array [100, 4, 200, 1, 3, 2], the longest consecutive sequence is [1, 2, 3, 4] and its length is 4.

Your solution should ideally have a time complexity of \(O(n)\) on average.

inputFormat

The input is given via standard input (stdin) with the following format:

• 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 consecutive elements sequence.

## sample

6
100 4 200 1 3 2

4

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