import sys
input = sys.stdin.readline

def main():
  n = int(input())
  vlist = list(map(int, input().split()))
  vlist = list(sorted(vlist, key=lambda x: -x))
  ans = 0
  for i, v in enumerate(vlist):
    print(i, v)
    ans += v / pow(2, i+1)
  ans += vlist[-1] / pow(2, len(vlist))
  print('%.10f' % ans)

if __name__ == '__main__':
  main()
