#include <bits/stdc++.h>
using namespace std;
const long long int mod = 1000000007, INF = 1099999999999999999;
void YES_OR_NO(bool check) {
  if (check) {
    cout << "YES" << endl;
  } else {
    cout << "NO" << endl;
  }
}
long long int m, k, n, a, b, res = 0, sum;
long double d[3000], dres = 0;
string str;
int main() {
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> d[i];
  }
  sort(d, d + n);
  dres = (d[0] + d[1]) / 2.0;
  for (int i = 2; i < n; i++) {
    dres = (dres + d[i]) / 2.0;
  }
  cout << dres << endl;
}
