#include <bits/stdc++.h>
int asc(const void* a, const void* b) { return *(double*)a - *(double*)b; }
int main(void) {
  int n;
  scanf("%d", &n);
  double v[10000];
  for (int i = 0; i < n; i++) {
    scanf("%lf", &v[i]);
  }
  qsort(v, sizeof(v) / sizeof(double), sizeof(double), asc);
  double sum = 0;
  int cnt = 0;
  double ans = (v[0] + v[1]) / 2;
  for (int i = 2; i < n; i++) {
    ans = (ans + v[i]) / 2;
  }
  printf("%.1f\n", ans);
  return 0;
}
