#include <bits/stdc++.h> using namespace std; int a[10001] = {3, 6}; int cnt; void brick(int n){ if(n == 1){ cout << "3"; }else if(n == 2){ cout << "6"; }else{ for(int i = 1; i <= n; i++){ a[i] = a[i - 1] + a[i - 2]; cnt = a[i]; } cout << cnt + 1; } } int main(){ int n; cin >> n; brick(n); return 0; }