#include <bits/stdc++.h>
using namespace std;
long long int N;
long long int arr[55];
long long int A, B;
int main() {
  scanf("%lld", &N);
  for (int i = 0; i < N; i++) {
    scanf("%lld", &arr[i]);
  }
  sort(arr, arr + N);
  int flag = 0;
  double sum = 0;
  for (int i = 1; i < N; i++) {
    if (i == 1) {
      A = arr[0];
    } else {
      A = sum;
    }
    B = arr[i];
    sum = (A + B) / 2.0;
  }
  printf("%0.12lf\n", sum);
  return 0;
}
