View Code of Problem 3692

#include<bits/stdc++.h>
using namespace std;
int main() {
	int N;
	long long arr[51];
	arr[1]=3;
	arr[2]=6;
	arr[3]=6; 
	for(int i=4; i<=50; i++) arr[i]=arr[i-1]*1+arr[i-2]*2;
	while(cin>>N) {
		cout<<arr[N]<<endl; 
	}
}