#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int N, tmp, i;
  cin >> N;
  int value[51];
  double min = 1001;
  for (i = 0; i < N; i++) {
    cin >> value[i];
    if (value[i] < min) {
      min = value[i];
      tmp = i;
    }
  }
  value[tmp] = 1002;
  while (N > 1) {
    int s_min = 1001, tmp2;
    for (int i = 0; i < N; i++) {
      if (value[i] <= s_min) {
        s_min = value[i];
        tmp2 = i;
      }
    }
    value[tmp2] = 1002;
    min = (min + (double)s_min) / 2;
    N--;
  }
  printf("%.5f", min);
  return 0;
}
