#include <iostream> using namespace std; int main() { int n; cin >> n; long long f[21], u[21], h[21]; f[0] = 1; u[0] = 1; h[0] = 0; for (int i = 1; i <= n; i++) { u[i] = f[i - 1]; h[i] = 2 * u[i - 1] + h[i - 1]; f[i] = u[i] + h[i]; } cout << f[n] << endl; return 0; }