#include <bits/stdc++.h>
using namespace std;
const int maxn = 2e9 + 9;
const int mod = 1e9 + 7;
long long GCD(long long a, long long b) { return b == 0 ? a : GCD(b, a % b); }
int main() {
  long long n, i;
  while (cin >> n) {
    double maxn = -1, minn = 2000, x;
    for (i = 0; i < n; i++) {
      cin >> x;
      maxn = maxn >= x ? maxn : x;
      minn = minn <= x ? minn : x;
    }
    double mid = (maxn + minn) / 2.0;
    printf("%.6lf\n", mid);
  }
}
