#include <bits/stdc++.h>
const double eps = 1e-8;
using namespace std;
inline long long read() {
  char ch = getchar();
  long long s = 0, w = 1;
  while (ch < 48 || ch > 57) {
    if (ch == '-') w = -1;
    ch = getchar();
  }
  while (ch >= 48 && ch <= 57) {
    s = (s << 1) + (s << 3) + (ch ^ 48);
    ch = getchar();
  }
  return s * w;
}
inline void write(long long x) {
  if (x < 0) putchar('-'), x = -x;
  if (x > 9) write(x / 10);
  putchar(x % 10 + 48);
}
priority_queue<double, vector<double>, greater<double> > q;
int main() {
  long long n = read();
  for (register long long i = 1; i <= n; i++) {
    double x = read();
    q.push(x);
  }
  double ans = 0;
  while (!q.empty()) {
    double a = q.top();
    q.pop();
    double b = q.top();
    q.pop();
    q.push((a + b) / 2.0);
    ans = (a + b) / 2;
  }
  cout << ans << "\n";
  return 0;
}
