#include <bits/stdc++.h>
using namespace std;
const int MOD = 1000000007;
long long gcd(long long x, long long y) {
  if (y == 0) return x;
  return gcd(y, x % y);
}
long long lcm(long long x, long long y) { return x * y / gcd(x, y); }
void solve(long long N, std::vector<long long> v) {
  long double min = 0, avg = 0, x, y;
  for (int i = 0; i < N - 1; i++) {
    auto itr_x = min_element(v.begin(), v.end());
    x = *itr_x;
    v.erase(itr_x);
    auto itr_y = min_element(v.begin(), v.end());
    y = *itr_y;
    v.erase(itr_y);
    avg = (x + y) / 2;
    v.push_back(avg);
  }
  cout << avg << endl;
}
int main() {
  long long N;
  scanf("%lld", &N);
  std::vector<long long> v(N);
  for (int i = 0; i < N; i++) {
    scanf("%lld", &v[i]);
  }
  solve(N, std::move(v));
  return 0;
}
