In how many ways can you tile a 3xn rectangle with 2x1 dominoes?

Here is a sample tiling of a 3x12 rectangle.

Input consists of several test cases followed by a line containing -1.
Each test case is a line containing an integer 0 ≤ n ≤ 30. For each test
case, output one integer number giving the number of possible tilings. 

SAMPLE INPUT

2
8
12
-1

SAMPLE OUTPUT

3
153
2131