#include <bits/stdc++.h>
using namespace std;
const double pi = acos(-1.0);
const long long mod = pow(10, 9) + 7;
const long long INF = pow(2, 31) - 1;
using str = string;
long long gcd(long long a, long long b) {
  long long v0 = a, v1 = b, v2 = a % b;
  while (v2 != 0) {
    v0 = v1;
    v1 = v2;
    v2 = v0 % v1;
  }
  return v1;
}
long long lcm(long long a, long long b) { return (a * b / gcd(a, b)); }
int main() {
  int n;
  cin >> n;
  vector<int> v(n);
  for (int i = 0; i < (n); i++) {
    cin >> v[i];
  }
  sort(v.begin(), v.end());
  float ans = (v[0] + v[1]) / 2;
  for (int i = 2; i < n; i++) {
    ans = (v[i] + ans) / 2;
  }
  printf("%.10f\n", ans);
  return 0;
}
