Problems
Tri Tiling
Tri Tiling
In how many ways can you tile a 3 x n rectangle with 2 x 1 dominoes? Here is a sample tiling of a 3 x 12 rectangle.
Input data
Consists of several test cases followed by a line containing -1. Each test case is a line containing an integer n (0 ≤ n ≤ 30).
Output data
For each test case print one integer giving the number of possible tilings.
Examples
Input example #1
2 8 12 -1
Output example #1
3 153 2131