my $location = $output_dir;
open LOGFILE, $location;

my $first_line = 1;
my $max_id;

while (<LOGFILE>) {
    if (/_(\d)+/) {
        if ($first_line) {
            $first_line = 0;
            $max_id = $1;
        } else {
            $max_id = $1 if ($1 > $max_id);
        }
    }
}