#include <bits/stdc++.h>
using namespace std;
int n, v[52];
double ans = 0;
int main() {
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> v[i];
    v[i] *= 2;
  }
  sort(v, v + n);
  for (int i = 1; i < n; i++) {
    v[i] = (v[i] + v[i - 1]) / 2;
  }
  cout << (double)v[n - 1] / 2.0 << endl;
  return 0;
}
