#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  float x;
  vector<float> v(n);
  for (int i = 0; i < n; i++) cin >> v[i];
  sort(v.begin(), v.end(), greater<int>());
  while (v.size() != 1) {
    int i = v.size() - 1;
    x = v[i] - (v[i] - v[i - 1]) / 2;
    v.pop_back();
    v.pop_back();
    v.push_back(x);
  }
  cout << fixed << setprecision(1) << v[0];
  return 0;
}
