#include <bits/stdc++.h>
using namespace std;
priority_queue<double, vector<double>, greater<double> > q;
int main(void) {
  int n;
  double m;
  double ans = 0;
  scanf("%d", &n);
  for (int i = 1; i <= n; i++) {
    scanf("%lf", &m);
    q.push(m);
  }
  while (q.size() != 1) {
    double a = q.top();
    q.pop();
    double b = q.top();
    q.pop();
    ans = (double)(a + b) * 0.5;
    q.push(ans);
  }
  printf("%.1lf", q.top());
  return 0;
}
