#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  scanf("%d", &n);
  vector<int> vectorV;
  for (int i = 0; i < n; i++) {
    int v;
    scanf("%d", &v);
    vectorV.push_back(v);
  }
  std::sort(vectorV.begin(), vectorV.end());
  float sumValue = 0;
  sumValue = (vectorV[0] + vectorV[1]) / 2;
  for (int i = 2; i < (int)vectorV.size(); ++i) {
    sumValue += vectorV[i];
    sumValue /= 2;
  }
  cout << sumValue << endl;
  return 0;
}
