#include <bits/stdc++.h>
using namespace std;
template <class T>
inline bool chmin(T& a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
long long N;
double v, tmp = 0;
priority_queue<long long, vector<long long>, greater<long long>> que;
signed main() {
  cin >> N;
  for (long long i = 0; i < (N); ++i) {
    cin >> v;
    que.push(v);
  }
  for (long long i = 0; i < N - 1; i++) {
    tmp = 0;
    tmp += que.top();
    que.pop();
    tmp += que.top();
    que.pop();
    que.push(tmp / 2.0);
  }
  printf("%.5f\n", tmp / 2.0);
  return 0;
}
