#include <bits/stdc++.h>
using namespace std;
int main() {
  int N, v[50], i;
  cin >> N;
  for (i = 0; i < N; i++) cin >> v[i];
  sort(v, v + N);
  float res = v[0];
  for (i = 1; i < N; i++) {
    res = (res + float(v[i])) / 2;
  }
  cout << res << endl;
}
