#include <bits/stdc++.h>

using namespace std;

int main() {
  int n;
  cin >> n;
  vector<double> a(n);
  for (int i = 0; i < n; ++i) cin >> a[i];

  sort(a.begin(), a.end());
  double ans;
  if (n % 2 == 0) {
    ans = (a[n / 2] + a[n / 2 - 1]) / 2;
  } else {
    ans = a[n / 2];
  }
  cout << fixed << setprecision(2) << ans << endl;
  return 0;
}