<?php
$n = trim(fgets(STDIN));
$a = explode(" ",trim(fgets(STDIN)));
$ans = 0;

sort($a);

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

echo $ans;
?>