#include <bits/stdc++.h>
double a_bs(double a) { return (a < 0) ? -a : a; }
using namespace std;
int main() {
  int n, cnt, mi_i, mi_j;
  cin >> n;
  double 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 = a_bs(v[1] - v[0]);
    mi_i = 1;
    mi_j = 0;
    for (int j = 0; j < cnt - 1; j++) {
      for (int k = 0; k < cnt - 1; k++) {
        if (j == k) continue;
        tmp = a_bs(v[j] - v[k]);
        if (tmp < min_abs) {
          min_abs = tmp;
          mi_i = j;
          mi_j = k;
        }
      }
    }
    v[mi_i] = (v[mi_i] + v[mi_j]) / 2.0;
    v[mi_j] = 100000000;
    cnt--;
  }
  sort(v, v + n);
  printf("%.7lf\n", v[0]);
}
