## Problem Description

A fractal is an object or quantity that displays self-similarity, in a somewhat technical
sense, on all scales. The object need not exhibit exactly the same structure at all scales, but
the same "type" of structures must appear on all scales.

A Sierpinski fractal is defined as below:

A Sierpinski fractal of degree 1 is simply
@

A Sierpinski fractal of degree 2 is
@
@@

If using B(n-1) to represent the Sierpinski fractal of degree n-1, then a Sierpinski fractal of degree n is defined recursively as following
B(n-1)
B(n-1)B(n-1)

Your task is to draw a Sierpinski fractal of degree n.

## Input

The input consists of several test cases. Each line of the input contains a positive integer n which is no greater than 10. The last line of input is an integer 0 indicating the end of input.

## Output

For each test case, output the Sierpinski fractal using the '@' notation. Print a blank line after each test case.
**Don't output any trailing spaces at the end of each line, or you may get a PE!**

## Sample Input

1
2
0

## Sample Output

@
@
@@

## Source

FOJ有奖月赛-2009年11月