#include <bits/stdc++.h>
using namespace std;
int top = -1;
double stc[10000];
void push(double x) {
  top++;
  stc[top] = x;
}
void pop() { top--; }
int main() {
  double n, v;
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> v;
    push(v);
  }
  while (top != 0) {
    v = (stc[top] + stc[top - 1]) / 2;
    top--;
    stc[top] = v;
  }
  printf("%.14lf\n", stc[top]);
  return 0;
}
