#include <bits/stdc++.h>
using namespace std;
int n;
double v[60], ans;
bool cmp(const double &a, const double &b) { return a > b; }
int main() {
  cin >> n;
  for (register int i = 1; i <= n; ++i) cin >> v[i];
  sort(v + 1, v + n + 1, cmp);
  ans = (v[1] + v[2]) / 2;
  for (register int i = 3; i <= n; ++i) ans = (ans + v[i]) / 2;
  cout << ans << endl;
  return 0;
}
