#include <bits/stdc++.h>
using namespace std;
const int MAXN = 60;
int n;
priority_queue<double> pq;
int main() {
  scanf("%d", &n);
  for (int i = 0; i < n; i++) {
    double ai;
    scanf("%lf", &ai);
    pq.push(ai);
  }
  double ans = 0;
  while ((int)pq.size() > 1) {
    double u = pq.top();
    pq.pop();
    double v = pq.top();
    pq.pop();
    ans = (u + v) / 2.0;
    pq.push(ans);
  }
  printf("%.5lf\n", ans);
}
