#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int a[n];
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  sort(a, a + n);
  float ans = (a[0] + a[1]) / 2.0;
  for (int i = 2; i < n; i++) {
    ans = (float)(a[i] + ans) / 2.0;
  }
  printf("%.1f", ans);
  return 0;
}
