<?php

$handle = fopen ("php://stdin","r");
fscanf($handle,"%d",$n);
$a_temp = fgets($handle);
$a = explode(" ",$a_temp);
array_walk($a,'intval');

$max = 0;
foreach ($a as $val) {
    $tmp = $tmp2 = 0;
    foreach ($a as $val2) {
        if ($val == $val2 || $val == $val2 + 1) {
            $tmp += 1;
        } elseif ($val == $val2 || $val == $val2 - 1) {
            $tmp2 += 1;
        }
    }
    if (max($tmp, $tmp2) > $max) {
        $max = max($tmp, $tmp2);
    }
}

print($max);

?>