#include <bits/stdc++.h>
long long int power(long long int a, long long int b) {
  long long int aa = 1;
  while (b) {
    if (b & 1) {
      aa = aa * a;
      aa %= 1000000007;
    }
    a = a * a;
    a %= 1000000007;
    b /= 2;
  }
  return aa;
}
using namespace std;
int main() {
  int n;
  cin >> n;
  long long int a[n];
  for (int i = 0; i < n; ++i) cin >> a[i];
  sort(a, a + n);
  long long int deno = (a[0] + a[1]) / 2.0;
  for (int i = 2; i < n; ++i) {
    deno = (a[i] + deno) / 2.0;
  }
  cout << setprecision(15) << deno << "\n";
}
