#include <bits/stdc++.h>
int main() {
  int in, k = 1;
  float v = 0;
  scanf("%d", &in);
  int a = 0;
  for (int i = 0; i < in; i++) {
    scanf("%d\n", &a);
    v += a;
  }
  printf("%.1f", v * in / (1 << in));
  return 0;
}
