#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  vector<int> vs;
  int v;
  for (int i = 0; i < N; ++i) {
    cin >> v;
    vs.push_back(v);
  }
  sort(vs.begin(), vs.end());
  for (int i = 0; i < N - 1; ++i) {
    vs[i + 1] = (double)vs[i] + (double)(vs[i + 1] - vs[i]) / (double)2;
  }
  cout << vs[N - 1] << endl;
  return 0;
}
