#include <bits/stdc++.h>
using namespace std;
typedef pair<int, int> XY;
int main() {
  int Nmax = 50;
  int V[Nmax];
  char String[Nmax];
  int N;
  int i, j, k;
  int len;
  int flag = 0;
  double tmp;
  scanf("%d", &N);
  for (i = 1; i <= N; i++) {
    scanf("%d ", &V[i]);
  }
  sort(V, V + N);
  tmp = V[1];
  for (i = 2; i <= N; i++) {
    tmp = (tmp + V[i]) / 2.0;
  }
  printf("%f\n", tmp);
  return 0;
}
