n = int(input())
numbers = list(map(int,input().split()))


def aaa(numbers):
    if len(numbers) > 1:
        numbers.sort()
        new_number = (numbers[0] + numbers[1]) / 2
        n_0 = numbers[0]
        n_1 = numbers[1]
        numbers.remove(n_0)
        numbers.remove(n_1)
        numbers.append(new_number)
        if len(numbers) > 1:
                return new_number
        else:
            aaa(numbers)
    else:
        return numbers[0]
      
aaa(numbers)