#include <bits/stdc++.h>
using namespace std;
long long n;
long long ans;
long long v[55];
int main() {
  scanf("%lld", &n);
  for (long long i = 0; i < n; i++) {
    scanf("%lld", &v[i]);
  }
  sort(v, v + n);
  ans += v[0];
  for (long long i = 1; i < n; i++) {
    ans += v[i] * (1 << (i - 1));
  }
  printf("%.9f", (double)ans / (1 << (n - 1)));
  return 0;
}
