#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  int v[51];
  float out = 0;
  cin >> N;
  for (int i = 0; i < N; i++) {
    v[i] = 0;
  }
  sort(v, v + N);
  out = (float)v[0];
  for (int i = 1; i < N; i++) {
    out = (out + v[i]) / 2;
  }
  cout << out;
  return 0;
}
