I - Tri Tiling

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

Submit Status

 #include<cstdio>
 using namespace std;
 int f(int n)
 {
     if(n==)
         return ;
     if(n==)
         return ;
     else
         return *f(n-)-f(n-);
 }
 int main()
 {
     int n;
     while(scanf("%d",&n)==&&n!=-)
         if(n%==)
         printf("%d\n",f(n));
         else
         printf("%d\n",);
     return ;
 }

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!