View Code of Problem 3692

#include<iostream>
#include<string>
#include<algorithm>
#include<cmath>
#include<vector>
#include<queue>
using namespace std;
int main()
{
	int N,i,j;
	long long f[51];
	f[1]=3,f[2]=6,f[3]=6;
	for( i=4;i<51;i++ ){
		f[i] = f[i-2]*2+f[i-1];
	}
	 while( cin>>N ){
	 	cout<<f[N]<<endl;
	 }
}