#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  scanf("%d", &N);
  int v[1001];
  for (int i = 0; i < N; i++) {
    scanf("%d", v + i);
  }
  sort(v, v + N);
  double ret = (double)(v[0] + v[1]) / 2.0l;
  double prev = ret;
  for (int i = 2; i < N; i++) {
    ret += (prev + (double)v[i]) / 2.0l;
  }
  printf("%lf", ret);
  return 0;
}
