Problem:
Score : 300 points

Problem Statement

You are given an integer sequence of length N, a_1,a_2,...,a_N.

For each 1≤i≤N, you have three choices: add 1 to a_i, subtract 1 from a_i or do nothing.

After these operations, you select an integer X and count the number of i such that a_i=X.

Maximize this count by making optimal choices.

Constraints

1≤N≤10^5

0≤a_i<10^5 (1≤i≤N)

a_i is an integer.

Input

The input is given from Standard Input in the following format:

N
a_1 a_2 .. a_N

Output

Print the maximum possible number of i such that a_i=X.

Sample Input 1

7
3 1 4 1 5 9 2

Sample Output 1

4

For example, turn the sequence into 2,2,3,2,6,9,2 and select X=2 to obtain 4, the maximum possible count.

Sample Input 2

10
0 1 2 3 4 5 6 7 8 9

Sample Output 2

3

Sample Input 3

1
99999

Sample Output 3

1

Solution in PHP7 (7.0.15) (judge verdict: Wrong Answer)

<?php
  fscanf(STDIN, "%d", $amout);  
  $array = explode(' ', fgets(STDIN));

  $counter = [];
  for($i=0 ; $i < $amout; $i++){
    $value = $array[$i];
	$counter[$value] = !array_key_exists($value, $counter) ? 1 : $counter[$value]++;
	$counter[$value+1] = !array_key_exists($value+1, $counter) ? 1 : $counter[$value+1]++;
    $counter[$value-1] = !array_key_exists($value-1, $counter) ? 1 : $counter[$value-1]++;
  }

 echo max($counter);