#include <bits/stdc++.h>
using namespace std;
int main() {
  int N, v[1005], i;
  double X;
  scanf("%d", &N);
  for (i = 0; i < N; i++) scanf("%d", &v[i]);
  sort(v, v + N);
  X = double((double)v[0] + (double)v[1]) / 2.0;
  for (i = 2; i < N; i++) X = double(X + (double)v[i]) / 2.0;
  printf("%f", X);
  return 0;
}
