#include <bits/stdc++.h>
int main() {
  int i, n;
  double val[1000], tmp;
  scanf("%d", &n);
  for (i = 0; i < n; i++) scanf("%lf", &val[i]);
  for (i = 0; i < n; i++) {
    for (int j = n - 1; j > i; j--) {
      if (val[j] < val[j - 1]) {
        tmp = val[j];
        val[j] = val[j - 1];
        val[j - 1] = tmp;
      }
    }
  }
  i = 0;
  while (i + 1 != n) {
    val[i + 1] = (val[i] + val[i + 1]) / 2;
  }
  printf("%f\n", val[n - 1]);
  return 0;
}
