#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int inf = 100000000;
int in() {
  int a;
  cin >> a;
  return a;
}
void forin(int* x, int y) {
  for (int i = 0; i < y; i++) {
    cin >> x[i];
  }
}
int intpow(int x, int y) {
  double a = x, b = y;
  return pow(a, b);
}
int intfabs(int x) {
  double a = x;
  return fabs(a);
}
int fact(int x) {
  if (x == 1) return 1;
  return x * fact(x - 1);
}
int fib(int x) {
  if (x <= 2) return x;
  int a[x];
  a[0] = 1;
  a[1] = 2;
  for (int i = 2; i < x; i++) {
    a[i] = a[i - 1] + a[i - 2];
  }
  return a[x - 1];
}
int div1(ll x) { return x % 1000000007; }
int main() {
  int n = in();
  vector<int> v(n);
  for (int i = 0; i < n; i++) cin >> v[i];
  sort(v.begin(), v.end());
  double pl = (v[0] + v[1]) / 2;
  for (int i = 2; i < n; i++) pl = (pl + v[i]) / 2;
  cout << pl << endl;
}
