#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  double ans = 0;
  cin >> n;
  vector<int> v(n);
  for (int i = 0; i < n; i++) cin >> v[i];
  sort((v).begin(), (v).end());
  for (int i = n - 2; i >= 0; i--) {
    if (v[i] == v[i + 1]) {
      v[i + 1] = 0;
    }
  }
  ans = v[0];
  for (int i = 1; i < n; i++) {
    if (v[i] != 0) {
      ans = (ans + v[i]) / 2;
    }
  }
  printf("%.12f\n", ans);
  return 0;
}
