#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 avg = v[0], x, y;
  if (N == 2) {
    cout << (v[0] + v[1]) / 2.0 << endl;
    return;
  }
  for (int i = 0; i < N - 1; i++) {
    sort(v.begin(), v.end());
    x = v[0];
    y = v[1];
    v.erase(v.begin());
    v.erase(v.begin());
    v.push_back((x + y) / 2.0);
  }
  cout << v[0] << 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;
}
