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

int main() {
    int N;
    double v;
    vector<double> vs;
    for (int i=0; i < N; ++i) {
        cin >> v;
        vs.push_back(v);
    }
    if (N == 1)
        return vs[0];
    make_heap(vs.begin(), vs.end());
    while (true) {
        double v1 = vs.front();
        pop_heap();
        double v2 = vs.front();
        pop_heap();
        double v3 = (v1 + v2) / 2.0;
        if (vs.empty()) {
            cout << v3 << endl;
            break;
        } else
        push_heap(vs, v3);
    }
    return 0;
}