Tri Tiling
Time Limit: 1 s
Memory Limit: 128 MB
Submission：23
AC：17
Score：99.81
Description
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.
Samples
input
2
8
12
-1
output
3
153
2131