#include <bits/stdc++.h>
void Swap(double x[], int i, int j) {
  int temp;
  temp = x[i];
  x[i] = x[j];
  x[j] = temp;
}
void QSort(double d[], int n) {
  for (int i = 0; i < n - 1; i++) {
    if (d[i] > d[i + 1]) {
      Swap(d, i, i + 1);
    }
  }
}
int main() {
  int n;
  double count = 0.0;
  scanf("%d", &n);
  double d[n];
  for (int i = 0; i < n; i++) {
    scanf("%lf", &d[i]);
  }
  QSort(d, n);
  for (int i = 0; i < n - 1; i++) {
    d[i + 1] = (d[i] + d[i + 1]) / 2;
  }
  printf("%lf", d[n - 1]);
}
