#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, m, i, j, k;
  double x, y, z;
  cin >> n;
  int a[n + 1];
  y = n;
  int b[n + 1];
  for (i = 1; i <= n; i++) {
    cin >> a[i];
    b[i] = a[i];
  }
  sort(a + 1, a + n + 1, greater<int>());
  if (n > 2) {
    x = (a[n] + a[n - 1]) / 2.0;
    for (i = n - 2; i > 0; i--) {
      x = (x + a[i]) / 2.0;
    }
    cout << x << endl;
  } else {
    cout << (a[0] + a[1]) / 2.0;
  }
}
