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!

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