#include <bits/stdc++.h>
int main() {
  int i, j, k = 1, N, mo = 1;
  int flag = 0;
  float u[101] = {0};
  float ans = 0;
  scanf("%d", &N);
  for (i = 0; i < N; i++) {
    scanf("%f", u + i);
    mo *= 2;
  }
  mo /= 2;
  for (i = 0; i < N; ++i) {
    for (j = i + 1; j < N; ++j) {
      if (u[i] > u[j]) {
        u[i] += u[j];
        u[j] = u[i] - u[j];
        u[i] = u[i] - u[j];
      }
    }
  }
  ans = u[0] / mo;
  for (i = 1; i < N; i++) {
    ans += u[i] / mo;
    mo /= 2;
  }
  printf("%f", ans);
  return 0;
}
