#include <bits/stdc++.h>
using namespace std;
int n, a[105];
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> n;
  for (int i = 1; i <= n; ++i) cin >> a[i];
  sort(a + 1, a + n + 1);
  cout << (a[n] + a[n - 1]) / 2 << ((a[n] + a[n - 1]) % 2 ? ".5" : "\n");
  return 0;
}
