#include <bits/stdc++.h>
using namespace std;
const int mod = 1e9 + 7;
int mul(int a, int b) { return (long long)a * b % mod; }
void add_self(int &a, int b) {
  a += b;
  if (a >= mod) a -= mod;
}
void mul_self(int &a, int b) { a = (long long)a * b % mod; }
void sub_self(int &a, int b) {
  a -= b;
  if (a < 0) a += mod;
}
int exp(int a, int b) {
  int ret = 1;
  while (b) {
    if (b % 2) {
      mul_self(ret, a);
    }
    mul_self(a, a);
    b /= 2;
  }
  return ret;
}
void solve() {
  int n;
  cin >> n;
  set<double> a;
  for (int i = 0; i < n; i++) {
    int num;
    cin >> num;
    a.insert(num);
  }
  while (((int)(a.size())) > 1) {
    auto it = a.begin();
    double x = *it;
    it++;
    double y = *it;
    a.erase(a.begin());
    a.erase(a.begin());
    a.insert((x + y) / 2);
  }
  printf("%.10lf\n", *(a.begin()));
}
int main() {
  clock_t beg = clock();
  solve();
  clock_t end = clock();
  fprintf(stderr, "%.2lf sec\n", (double)(end - beg) / CLOCKS_PER_SEC);
}
