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