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 PHP (5.6.30) (judge verdict: Accepted)

<?php
error_reporting(0);
//list($x,$t) = explode(" ",trim(fgets(STDIN)));
$N = trim(fgets(STDIN));
$a = explode(" ",trim(fgets(STDIN)));
$v = array_count_values($a);
ksort($v);
$maxpos = 0;
$max=1;
$maxwk=0;
foreach($v as $k=>$vv) {
  $maxwk = $vv;
  $flg = 0;
  for($i=$k+1;$i<$k+3;$i++) {
    if (array_key_exists($i,$v)) {
      $maxwk += $v[$i];
    }
  }
  if ($maxwk > $max) {
    $max = $maxwk;
  }
}
printf("%d\n",$max);