#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int m = n;
  float a[n];
  float ans;
  for (int i = 0; i < n; i++) cin >> a[i];
  int min1 = 999999, min2 = 999999, index1, index2;
  while (m > 1) {
    min1 = 999999;
    min2 = 999999;
    for (int i = 0; i < n; i++) {
      if (min1 > a[i]) {
        min1 = a[i];
        index1 = i;
      }
    }
    int fixer = a[index1];
    a[index1] = 999999;
    for (int i = 0; i < n; i++) {
      if (min2 > a[i] && min1 != min2) {
        min2 = a[i];
        index2 = i;
      }
    }
    a[index1] = fixer;
    ans = min1 + min2;
    ans = ans / 2;
    if (index1 < index2) {
      a[index1] = ans;
      a[index2] = 999999;
    } else {
      a[index2] = ans;
      a[index1] = 999999;
    }
    m--;
  }
  cout << ans;
  return 0;
}
