#include "bits/stdc++.h"

#define REP(i, a, b) for (int i = (a); i <= (b); ++i)
#define REV(i, a, b) for (int i = (a); i >= (b); --i)
#define FORV(a, A) for (auto &a : A)

using ll = long long;

using namespace std;

void Main()
{
   int N;
   cin >> N;
   set<int> V;
   int v;
   REP(i,0,N-1)
   {
      cin >> v;
      V.insert(v);
   }
   double ans = 0;
   int i=1;
   for(auto v=V.begin();v!=V.end();v++)
   {
      if(i)
      {
         ans += *v;
         i = 0;
         continue;
      }
      ans += *v;
      ans/=2.0;
   }
   cout << ans << endl;
   return;
}

int main()
{
   std::cin.tie(nullptr);
   std::ios_base::sync_with_stdio(false);
   std::cout << std::fixed << std::setprecision(15);
   Main();
   return 0;
}
}