hdu 1143 Tri Tiling

Tri Tiling

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)

Total Submission(s): 2125 Accepted Submission(s): 1215



Problem 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

#include <iostream>
using namespace std;
int main()
{
int f[31]={0};
f[0]=1;
f[2]=3;
for (int i=4; i<31; i+=2)
{
f[i]=4*f[i-2]-f[i-4];
}
int n;
while (cin>>n  && n>=0)
{
cout<<f
<<endl;
}
return 0;
}