#include <bits/stdc++.h>
int main() {
  int n;
  scanf("%d", &n);
  unsigned long long v[50];
  for (int i = 0; i < n; ++i) {
    scanf("%lld", v + i);
  }
  std::sort(v, v + n);
  double ans = *v / (1 << (n - 1));
  for (int i = 1; i < n; ++i) {
    ans += v[i] * (1 << (i - 1)) / (1 << (n - 1));
  }
  printf("%f\n", ans);
  return 0;
}
