#include <bits/stdc++.h>
using namespace std;
long long i, j;
int main() {
  long long n;
  cin >> n;
  vector<long long> v(n);
  for (long long i = 0; i < n; i++) cin >> v[i];
  sort(v.begin(), v.end());
  float sum = 0;
  float x = (v[0] + v[1]) / 2;
  for (i = 2; i < n; i++) {
    x = (x + v[i]) / 2;
  }
  cout << setprecision(9) << x << fixed << '\n';
  return 0;
}
