#include <bits/stdc++.h>
using namespace std;
const int MAX = 55;
const int INF = 1e9;
const int MOD = 1e9 + 7;
int N;
int main() {
  cin >> N;
  vector<double> v(N);
  for (int i = 0; i < (N); ++i) cin >> v[i];
  while (1 < v.size()) {
    sort(v.begin(), v.end());
    int a, b;
    a = v[0];
    b = v[1];
    v.erase(v.begin(), v.begin() + 2);
    v.push_back((double)(a + b) / 2.0);
  }
  cout << v[0] << endl;
}
