Problem Statement

The main occupation of the citizens of Numberland is to perform tasks on numbers, One such important task is finding interesting number sequences.

As per the Numberland institute of Research, an interesting sequence is defined as a sequence of numbers that are consecutive, for example:

$123456$

$10,11,12,13$

are interesting sequences. Mathematically, an interesting sequence has the following generic property: $n_i+1=n_{i+1}$

The task faced by the research institute is as follows:

Given an ordered set of distinct numbers, extract the length

of the largest interesting sequence that can be obtained

by rearranging the set of numbers.

Help the research institute in finding the longest interesting subsequences.

Input Format

The input consists of two lines.

The first line contains $N,$ the length of the input sequence.

The second line of input consists of $N$ numbers, the sequence of numbers that must be analyzed.