#include <bits/stdc++.h>
const int dx[8] = {1, 0, -1, 0, 1, -1, -1, 1};
const int dy[8] = {0, 1, 0, -1, 1, 1, -1, -1};
const int dr[4] = {-1, 0, 1, 0};
const int dc[4] = {0, 1, 0, -1};
const int INF = 1e9;
int guki(int a) {
  if (a % 2 == 0)
    return 0;
  else
    return 1;
}
int gcd(int a, int b) {
  if (a % b == 0) {
    return b;
  } else {
    return (gcd(b, a % b));
  }
}
int lcm(int a, int b) {
  int x = gcd(a, b);
  return (a * b / x);
}
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<double> vec(n);
  for (int i = (int)(0); i < (int)(n); ++i) {
    cin >> vec[i];
  }
  while (n != 1) {
    sort(vec.begin(), vec.end());
    vector<double> dif(n);
    pair<int, double> mm;
    for (int i = (int)(0); i < (int)(n - 1); ++i) {
      if (vec[i + 1] == INF)
        break;
      else {
        dif[i] = vec[i + 1] - vec[i];
        if (i == 0) {
          mm.first = i;
          mm.second = dif[i];
        } else {
          if (mm.second > dif[i]) {
            mm.second = dif[i];
            mm.first = i;
          }
        }
      }
    }
    vec[mm.first] += mm.second / 2;
    vec[mm.first + 1] = INF;
    n--;
  }
  cout << vec[0] << endl;
}
