#include <bits/stdc++.h>
int main() {
  int num = 0, i = 0, j = 0, temp = 0;
  double ans = 0.0, kao = 0.0;
  scanf("%d", &num);
  double yoshio[num];
  for (i = 0; i < num; i++) {
    scanf("%d", yoshio[i]);
  }
  for (i = 0; i < num - 1; i++) {
    for (j = i + 1; j < num; j++) {
      if (yoshio[i] > yoshio[j]) {
        temp = yoshio[j];
        yoshio[j] = yoshio[i];
        yoshio[i] = temp;
      }
    }
  }
  kao = yoshio[0];
  for (i = 1; i < num; i++) {
    kao = (kao + yoshio[i]) / 2;
  }
  printf("%lf\n", kao);
  return 0;
}
