#define pb push_back
#define ppb pop_back
#define INF 1e18
typedef long long ll;

using namespace std;

int main(int argc,char* argv[])
{
    int n;
    cin >> n;
    vector<double> v(n);
    rep(i, n) cin >> v[i];
    sort(all(v));
    double sum = (v[0]+v[1])/2;
    for (int i = 2; i < n; i++)
    {
        sum = (sum+v[i])/2;
    }
    cout << sum << endl;
    return 0;
}