#include <algorithm>
#include <functional>
#include <iostream>
#include <vector>
using namespace std;

int main() {
    int n;
    cin >> n;
    auto v = vector<double>(n);
    for (auto &v_i : v)
        double v_i;

    while (v.size() >= 2) {
        sort(v.begin(), v.end(), greater<double>());
        auto a = v.back();
        v.pop_back();
        auto b = v.back();
        v.pop_back();
        v.push_back((a + b) * 0.5);
    }

    printf("%.10f\n", v.front());
    return 0;
}
