#include <bits/stdc++.h>
using namespace std;
int a[1100];
int main() {
  int n;
  int x;
  double ans = 0;
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> a[i];
  }
  sort(a + 1, a + 1 + n);
  if (n == 2)
    ans = 1.0 * (a[1] + a[2]) / 2;
  else {
    ans = (a[1] + a[2]) / 2;
    for (int i = 3; i <= n; i++) ans = (ans + a[i]) / 2;
  }
  cout << ans << '\n';
  return 0;
}
