#include <bits/stdc++.h>
using namespace std;
#define FOR(i, a, b) for(int i=(a);i<(b);++i)
#define rep(i, n) FOR(i, 0, n)
#define whole(x) (x).begin(),(x).end()
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end())
using ll = long long;
using P = pair<int, int>;
const int mod = 1000000007;

int main()
{
  int n;
  cin >> n;
  vector<int> v(n);
  rep(i, n) cin >> v[i];
  sort(v.begin(), v.end());
  double ans = 0.5 * (v[0] + v[1]);
  rep(i, n) {
    if (i==0 || i==1) continue;
    ans = 0.5 * (ans+a[i]);
  }
  printf("%.10f", ans);
  return 0;
}