#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  double a[1010], b = 0;
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  sort(a, a + n);
  if (n == 2) {
    cout << (a[0] + a[1]) / 2 << "\n";
  } else {
    b = (a[0] + a[1]) / 2;
    cout << (b + a[2]) / 2 << "\n";
  }
}
