AMZSEQ
#include<iostream>
using namespace std;
typedef long long int int64;
int main()
{
int64 arr[10000];
arr[1] = 3;
arr[2] = 7;
int i = 2;
while(arr[i]<1e10)
{
arr[i+1] = 2*arr[i] + arr[i-1];
i++;
}
int n;
cin>>n;
cout<<arr[n]<<endl;
}
#include<iostream>
using namespace std;
typedef long long int int64;
int main()
{
int64 arr[10000];
arr[1] = 3;
arr[2] = 7;
int i = 2;
while(arr[i]<1e10)
{
arr[i+1] = 2*arr[i] + arr[i-1];
i++;
}
int n;
cin>>n;
cout<<arr[n]<<endl;
}