my $i = int(($l/24 + $u/24) / 2) * 24;
sysseek($fh, $i, SEEK_SET) or croak "seek: $!";
sysread($fh, my $buf, 24) == 24 or croak "read: $!";
- my ($r, $c) = unpack('NH40', $buf);
+ my ($r, $c) = unpack(rev_map_fmt, $buf);
if ($r < $rev) {
$l = $i + 24;