use strict;
use warnings;

my $n = shift;
my $count = 1;
my @matrix;

push @matrix, [(0)] for (1..$n);
buildRing (0, $n - 1);
my $width = length sprintf ("%s", '' . $count);
my $format = "%${width}d";
print "" . (join " ", map {sprintf $format, $_} @{$matrix[$_]}) . "\n" for (0..($n-1));


sub buildRing
{
my ($first, $last) = @_;
$matrix[$first][$_] = $count++ for ($first..$last);
$matrix[$_][$last] = $count++ for (($first+1)..$last);
$matrix[$last][$last-$_+$first-1] = $count++ for ($first..$last-1);
for ($_ = --$last; $_ > $first; --$_)
  {$matrix[$_][$first] = $count++}
$matrix[$first][$last] = $count if (++$first == $last);
buildRing ($first, $last) if ($first<$last);
}