#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  double numArr[n];
  int index = 0;
  while (n != index) {
    int input;
    cin >> input;
    numArr[index] = input;
    index += 1;
  }
  sort(numArr, numArr + n);
  for (int i = 0; i < n - 1; ++i) {
    double first = numArr[i] + numArr[i + 1];
    numArr[i + 1] = first / 2;
  }
  cout << numArr[n];
  return 0;
}
