#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  double v;
  vector<double> vs;
  for (int i = 0; i < N; ++i) {
    cin >> v;
    vs.push_back(v);
  }
  if (N == 1) return vs[0];
  make_heap(vs.begin(), vs.end());
  while (true) {
    double v1 = vs.front();
    pop_heap(vs.begin(), vs.end());
    double v2 = vs.front();
    pop_heap(vs.begin(), vs.end());
    double v3 = (v1 + v2) / 2.0;
    if (vs.empty()) {
      cout << v3 << endl;
      break;
    } else
      vs.push_back(v3);
    push_heap(vs.begin(), vs.end());
  }
  return 0;
}
