I - Tri Tiling

 

Time Limit:1000MS     Memory Limit:65536KB     64bit IO Format:%I64d & %I64u

Submit  Status

 1 #include<cstdio>

 2 using namespace std;

 3 int f(int n)

 4 {

 5     if(n==0)

 6         return 1;

 7     if(n==2)

 8         return 3;

 9     else

10         return 4*f(n-2)-f(n-4);

11 }

12 int main()

13 {

14     int n;

15     while(scanf("%d",&n)==1&&n!=-1)

16         if(n%2==0)

17         printf("%d\n",f(n));

18         else

19         printf("%d\n",0);

20     return 0;

21 }

 

Description

In how many ways can you tile a 3xn rectangle with 2x1 dominoes?   Here is a sample tiling of a 3x12 rectangle. 

Input

Input consists of several test cases followed by a line containing -1. Each test case is a line containing an integer 0 <= n <= 30.

Output

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



DP!