#include <bits/stdc++.h>
int main() {
  int n;
  scanf("%d", &n);
  int v[n];
  for (int i = 0; i < n; i++) {
    scanf("%d", &v[i]);
  }
  for (int i = 1; i < n; i++) {
    for (int j = 0; j < n; j++) {
      if (v[j] > v[j + 1]) {
        int tmp = v[j];
        v[j] = v[j + 1];
        v[j + 1] = tmp;
      }
    }
  }
  double point = (double)v[0];
  for (int i = 1; i < n; i++) {
    point = ((point + (double)v[i]) / 2);
  }
  printf("%lf", point);
  return 0;
}
