#include <bits/stdc++.h>
using namespace std;
int main() {
  int N, i, num;
  double result;
  cin >> N;
  if (N >= 2 && N <= 50) {
    int A[N];
    for (i = 0; i < N; i++) {
      cin >> A[i];
      if (A[i] <= 1 || A[i] >= 1000) {
        exit(0);
      }
    }
    sort(A, A + N);
    result = A[0];
    for (unsigned int i = 1; i < N; i++) {
      result = (result + A[i]) / 2;
    }
    cout << fixed << setprecision(5) << result << endl;
  }
  return 0;
}
