Python Online o'quv markazi ma'lumot guruhi
#D
n,k = map(int, input().split())
hodimlar = list(map(int, input().split()))
def max_average_subarray(nums, k):
n = len(nums)
sum_ = sum(nums[:k])
max_sum = sum_
for i in range(k, n):
sum_ += nums[i] - nums[i-k]
max_sum = max(max_sum, sum_)
return max_sum / k
print(max_average_subarray(hodimlar, k))