#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main() {
  ll N;
  cin >> N;
  double b[N];
  double mb = 0;
  long long ma = 0;
  for (long long i = 0; i < N; i++) {
    cin >> b[i];
  }
  sort(b, b + N);
  mb = (b[0] + b[1]) / 2;
  for (long long i = 2; i < N; i++) {
    if (mb <= b[i + 1]) {
      mb = (mb + b[i]) / 2;
    } else {
      ma = 0;
    }
  }
  cout << mb << endl;
}
