#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, cnt, mi_ind;
  cin >> n;
  double sum = 0, v[n], tmp, min_abs;
  cnt = n;
  for (int i = 0; i < n; i++) {
    cin >> v[i];
  }
  for (int i = 0; i < n - 1; i++) {
    sort(v, v + n);
    min_abs = abs(v[1] - v[0]);
    mi_ind = 0;
    for (int j = 0; j < cnt - 1; j++) {
      tmp = abs(v[j] - v[j + 1]);
      if (tmp < min_abs) {
        min_abs = tmp;
        mi_ind = j;
      }
    }
    v[mi_ind] = (v[mi_ind] + v[mi_ind + 1]) / 2.0;
    v[mi_ind + 1] = 100000000;
    cnt--;
  }
  sort(v, v + n);
  printf("%.7lf\n", v[0]);
}
