#include <iostream>

typedef long long ll;

const ll mod = ll(1e9)+7;

int main() {
	ll a = 1, b = 0, n;
	
	std::cin >> n;
	
	for (ll i = 0; i < n; ++i) {
		ll new_a = a * 3 + b;
		ll new_b = b * 3 + a;
		a = new_a;
		b = new_b;
	}
	
	std::cout << a;
	
	return 0;
}