#include <bits/stdc++.h>
using namespace std;
const int dx[] = {1, 0, -1, 0, 1, 1, -1, -1},
          dy[] = {0, -1, 0, 1, 1, -1, 1, -1};
const long long MOD = 1e9 + 7;
template <typename T>
inline T GCD(T a, T b) {
  T c;
  while (b != 0) {
    c = a % b;
    a = b;
    b = c;
  }
  return a;
}
template <typename T>
inline T LCM(T a, T b) {
  T c = GCD(a, b);
  a /= c;
  return a * b;
}
template <typename T>
inline T nCr(T a, T b) {
  T i, r = 1;
  for (i = 1; i <= b; i++) {
    r *= (a + 1 - i);
    r /= i;
  }
  return r;
}
template <typename T>
inline T nHr(T a, T b) {
  return nCr(a + b - 1, b);
}
signed main(void) {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int_fast64_t N;
  cin >> N;
  vector<double> v(N);
  for (int_fast64_t i = 0; i < (N); ++i) cin >> v[i];
  sort((v).begin(), (v).end());
  for (int_fast64_t q = 0; q < (N - 1); ++q) {
    double mn = 10000000.0;
    int_fast64_t fir, sec;
    for (int_fast64_t i = 0; i < (v.size() - 1); ++i) {
      for (int_fast64_t j = i + 1; j < v.size(); j++) {
        if (mn > (v[j] - v[i])) {
          mn = v[j] - v[i];
          fir = i;
          sec = j;
        }
      }
    }
    double tmp = (v[fir] + v[sec]) / 2.0;
    v.erase(v.begin() + sec);
    v.erase(v.begin() + fir);
    v.emplace_back(tmp);
    sort((v).begin(), (v).end());
  }
  cout << fixed << setprecision(15) << v[0] << '\n';
}
