#include <bits/stdc++.h>
int main(void) {
  int N, i;
  double ans;
  scanf("%d", &N);
  int v[N];
  for (i = 0; i < N; i++) {
    scanf("%d", &v[i]);
  }
  int v_min = 1001, cnt_1, cnt_2, v_sort[N];
  for (cnt_1 = 0; cnt_1 < N; cnt_1++) {
    for (cnt_2 = 0; cnt_2 < N; cnt_2++) {
      if (v_min > v[cnt_2]) {
        v_min = v[cnt_2];
        v[cnt_2] = 10000;
      }
    }
    v_sort[cnt_1] = v_min;
    v_min = 1001;
  }
  ans = (v_sort[0] + v_sort[1]);
  ans = ans / 2;
  for (i = 2; i < N; i++) {
    ans = (ans + v_sort[i]) / 2;
  }
  printf("%lf", ans);
  return 0;
}
