$N=<>;
for(1..$N**2){
	$_[$y][$x]=sprintf'%03d',$_;
	$t=$x+(1,0,-1,0)[$d];
	$u=$y+(0,1,0,-1)[$d];
	if($t>=$N||$u>=$N||$_[$u][$t]){
		$d=$d+1&3;
	}
	$x+=(1,0,-1,0)[$d];
	$y+=(0,1,0,-1)[$d];
}
print"@$_\n"for@_