#include <bits/stdc++.h>
using namespace std;
int niz[100];
int main() {
  ios_base::sync_with_stdio(false);
  cout.precision(10);
  cout << fixed;
  int n;
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> niz[i];
  }
  sort(niz + 1, niz + 1 + n);
  long double res = 0;
  for (int i = 1; i <= n; i++) {
    res = (res + niz[i]) / 2;
  }
  cout << res;
  return 0;
}
