#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  scanf("%d", &n);
  int a[n + 1];
  for (int i = 1; i <= n; i++) {
    scanf("%d", &a[i]);
  }
  sort(a + 1, a + n + 1);
  for (int i = 2; i <= n; i++) {
    a[i] = (a[i - 1] + a[i]) * 1.0 / 2;
  }
  if (a[n] == (int)a[n])
    cout << (int)a[n];
  else {
    cout << fixed << setprecision(1) << a[n];
  }
  return 0;
}
