<?php
$n = trim(fgets(STDIN));
$ans = 1;

for ($i = 0; $i < $n; $i++) {
     $a[] = trim(fgets(STDIN)); 
}

rsort($a);

for ($j = 1; $j < $n; $j++) {
     if($a[$j]+1 >= $a[$j-1]){
         $ans++;
     }
}

echo $ans;
?>