#include <bits/stdc++.h>
using namespace std;
#include <boost/multiprecision/cpp_dec_float.hpp>
using namespace boost::multiprecision;

int main() {
  int N;
  cin >> N;
  cpp_dec_float_100 f = 4;
  for (int i = 0; i < N; i++) f *= 0.75;
  cout << fixed << setprecision(9) << f << "\n";
}