#include <bits/stdc++.h>
using namespace std;
float mix(float x = 0, float y = 0) {
  float res = (x + y) / 2;
  return res;
}
int main() {
  cin.tie(0);
  ios_base::sync_with_stdio(0);
  int n = 0;
  cin >> n;
  vector<float> nums(n);
  for (int i = 0; i < n; i++) {
    cin >> nums[i];
  }
  while (nums.size() >= 2) {
    sort(nums.begin(), nums.end());
    float first = nums[0];
    float last = nums[1];
    nums.erase(nums.begin() + 0, nums.begin() + 2);
    nums.push_back(mix(first, last));
  }
  cout << nums[0];
  return 0;
}
