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
// Try AtCoder
// author: Leonardone @ NEETSDKASU

function gets() { return trim(fgets(STDIN)); }
function getVals() { return explode(' ', gets()); }
function getInts() { return array_map(intval, getVals()); }

$N = intval(gets());
$xs = getInts();

$tb = array_fill(0, 100003, 0);

foreach ($xs as $x) {
    for ($i = $x; $i <= $x+2; $i++) {
        $tb[$i]++;
    }
}

sort($tb);

echo $tb[100002], PHP_EOL;