#include <iostream>
#include <iomanip>
#include <algorithm>
#include <vector>

using ldouble = long double;

void solve() {
    int n;
    std::cin >> n;

    std::vector<int> xs(n * 2);
    for (int i = 0; i < n; ++i) {
        std::cin >> xs[i * 2];
        xs[i * 2 + 1] = xs[i * 2];
    }

    std::sort(xs.begin(), xs.end());
    int s = xs[n - 1] + xs[n];

    std::cout << std::fixed << std::setprecision(1)
              << ldouble(s) / 2 << std::endl;
}

int main() {
    std::cin.tie(nullptr);
    std::cout.tie(nullptr);
    std::ios::sync_with_stdio(false);

    solve();

    return 0;
}