#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, A[110];
  float sum;
  cin >> a;
  for (int i = 0; i < a; ++i) {
    cin >> A[i];
  }
  sort(A, A + a);
  reverse(A, A + a);
  if (a > 2) {
    sum += (A[1] + A[2]) / 2.0;
    for (int i = 3; i < a; i++) {
      sum = (A[i] + sum) / 2.0;
    }
    sum = (A[0] + sum) / 2.0;
  } else {
    sum = (A[0] + A[1]) / 2.0;
  }
  cout << sum;
  return 0;
}
