#include <bits/stdc++.h>
using namespace std;
const int INF = 1e9 + 10;
int dx[5] = {0, 0, 1, -1, 0}, dy[5] = {1, -1, 0, 0, 0};
const double EPS = 1e-10;
bool cmp(pair<int, int> a, pair<int, int> b) { return a.second < b.second; }
long long MOD = 1e9 + 7;
int n;
double v[60];
double ans;
int main(void) {
  cin >> n;
  for (int i = 0; i < n; i++) cin >> v[i];
  sort(v, v + n);
  long long sum = 0;
  long long pow = 1;
  for (int i = 0; i < n; i++) {
    if (i > 1) pow *= 2;
    sum += pow * v[i];
  }
  cout << " sum is : " << sum << endl;
  printf("%.8f\n", (double)sum / (2 * pow));
  return 0;
}
