#include <bits/stdc++.h>
int main(void) {
  int N, n, flag;
  double buf;
  double* v;
  scanf("%d", &N);
  v = (double*)malloc(sizeof(double) * N);
  for (int i = 0; i < N; i++) {
    scanf("%lf", &v[i]);
  }
  for (int i = 0; i < (N - 1); i++) {
    n = N;
    do {
      flag = 0;
      n--;
      for (int j = i; j < n; j++) {
        if (v[i] > v[j + 1]) {
          buf = v[j];
          v[j] = v[j + 1];
          v[j + 1] = buf;
          flag = 1;
        }
      }
    } while (flag == 1);
    v[i + 1] = (v[i] + v[i + 1]) / 2.0;
  }
  printf("%lf\n", v[N - 1]);
  free(v);
  return 0;
}
