#include <iostream>
#include <iomanip>

using namespace std;

int main(int argc, char *argv[])
{
  int n;
  cin >> n;
  double ret = 4.0;

  for (int i = 0; i < n; i++)
    ret = ret * 3 / 4;
  
  cout << fixed << setprecision(15) << ret << endl;
  return 0;
}