#include<bits/stdc++.h> using namespace std; long long a[55]; int main(){ a[0]=3; a[1]=6; a[2]=6; int n;cin>>n; for(int i= 3;i<=n;i++){ a[i]=a[i-1]+a[i-2]*2; } cout<<a[n-1]; }

#include<bits/stdc++.h> using namespace std; int main(){ int n; cin >> n; long long a[100005] = {}; a[1] = 0, a[2] = 6, a[3] = 6; for(int i = 4; i <= n; i++){ a[i] = a[i-1] + a[i-2] * 2; } cout << a[n]; return 0; }