hdu 2047 阿牛的EOF牛肉串

#include <iostream>
using namespace std;
int main()
{   int n;long long num[40] = {0,3,8};for(int i=3;i<40;i++){num[i] = (num[i-2]+num[i-1])*2;}while(cin>>n){cout<<num[n]<<endl;}return 0;
}