#include <bits/stdc++.h>
using namespace std;

using ld = long double;

int main(void) {
	cout << fixed << setprecision(30);
	int N;
	cin >> N;
	
	if(N == 0) {
		cout << 4 << "\n";
		return 0;
	}
	
	vector<ld> A(N + 1, 0);
	A[0] = 4, A[1] = 3;
	
	for(int i = 2; i <= N; ++i) {
		A[i] = (A[i - 1] * 19 - A[i - 2] * 12) / 4;
	}
	
	cout << A[N] << "\n";
	
	return 0;
}