#include <bits/stdc++.h> using namespace std; int temp = 0; void move(int n, char a, char b, char c) { if (n == 0) { return; } move(n - 1, a, c, b); temp++; move(n - 1, b, a, c); } int main() { int n; char a = 'A', b = 'B', c = 'C'; cin >> n; move(n, a, b, c); cout << temp << endl; return 0; }