#include <bits/stdc++.h>
using namespace std;
int main(void) {
  int N;
  cin >> N;
  float V[N];
  for (int i = 0; i < N; i++) {
    cin >> V[i];
  }
  for (int i = N - 1; i >= 0; i--) {
    sort(V + 0, V + i);
    V[i - 1] = (V[i] + V[i - 1]) / 2;
  }
  cout << V[0];
  return 0;
}
