#include <iostream>

using namespace std;

int main() {
  
  int N; cin >> N;
  double a[110];
  a[0] = 4;//, a[1] = 3;
  for(int i=1;i<110;i++) a[i] = a[i-1]*0.75;
  printf("%.15f\n", a[N]);
  return 0;
}