#include <bits/stdc++.h>
using namespace std;
int n, now;
double a[51], b[51];
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  cin >> n;
  now = n;
  for (int i = 1; i <= n; ++i) cin >> a[i];
  for (int k = 1; k < n; ++k) {
    sort(a + 1, a + now + 1);
    double minn = 0x3f3f3f3f;
    int p;
    for (int i = 2; i <= now; ++i)
      if (a[i] - a[i - 1] <= minn) {
        minn = a[i] - a[i - 1];
        p = i;
      }
    double t = (a[p] + a[p - 1]) / 2.0;
    a[p - 1] = t;
    for (int i = p; i <= now; ++i) a[i] = a[i + 1];
    --now;
  }
  cout << a[1];
  return 0;
}
