#include <bits/stdc++.h>
int main() {
  long n, v[1005], i, j, k, m, f = 1;
  scanf("%ld", &n);
  for (i = 0; i < n; i++) {
    scanf("%ld", &v[i]);
    v[i] <<= (n - 1);
  }
  while (f == 1) {
    f = 0;
    for (i = 0; i < n - 1; i++) {
      if (v[i] < v[i + 1]) {
        k = v[i];
        v[i] = v[i + 1];
        v[i + 1] = k;
        f = 1;
      }
    }
  }
  for (i = n - 1; i > 0; i--) {
    v[i - 1] += v[i];
    v[i - 1] >>= 1;
  }
  printf("%ld.", v[0] >> (n - 1));
  v[0] &= (1 << (n - 1)) - 1;
  for (i = 0; i <= 6; i++) {
    v[0] *= 10;
    printf("%ld", v[0] >> (n - 1));
    v[0] &= (1 << (n - 1)) - 1;
  }
  return (0);
}
