#include <bits/stdc++.h>
using namespace std;
double f(int x, int y) { return (x + y) / 2.0; }
int main() {
  int n;
  cin >> n;
  double sum;
  int a[55] = {0};
  for (int i = 0; i < n; i++) cin >> a[i];
  sort(a, a + n);
  sum = f(a[0], a[1]);
  for (int i = 2; i < n; i++) sum = f(sum, a[i]);
  cout << sum;
  return 0;
}
