#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <utility>
#include <cmath>

using namespace std;

int main() {
	int n;

	cin >> n;
	// 漸化式をとくと　Ak = 4 * (3/ 4)^k
	printf("%.50f\n", 4.0 * pow(0.75, n));
	return 0;
}