#include <bits/stdc++.h>
int cmpfunc(const void* a, const void* b) { return (*(int*)a - *(int*)b); }
int main(void) {
  int N;
  scanf("%d", &N);
  int array[N];
  for (int i = 0; i < N; i++) scanf("%d", &array[i]);
  qsort(array, N, sizeof(int), cmpfunc);
  int i = 0;
  float sum = (float)(array[i] + array[i + 1]) / 2;
  for (int i = 1; i < N - 1; i++) {
    sum = (sum + (float)array[i + 1]) / 2;
  }
  printf("%.1f", sum);
  return EXIT_SUCCESS;
}
