#include <bits/stdc++.h>
int main() {
  int n;
  scanf("%d", &n);
  int v[50];
  for (int i = 0; i < n; ++i) {
    scanf("%d", v + i);
  }
  std::sort(v, v + n);
  double ans = (*v + *(v + 1)) / 2;
  for (int i = 2; i < n; ++i) {
    ans = (ans + v[i]) / 2;
  }
  printf("%f\n", ans);
  return 0;
}
