n, k = map(int, input().split())
p = list(map(int, input().split()))

p = list(map(lambda x: (1+x)/2, p))
s = [0]
num = 0
for i in range(n):
  num += p[i]
  s.append(num)
l = []
for i in range(n - k + 1):
  l.append(s[i+k]-s[i])

print(max(l)) n, k = map(int, input().split()) n map(int, input().split()) map int input().split() ().split () input split k p = list(map(int, input().split())) p list(map(int, input().split())) list map(int, input().split()) map int input().split() ().split () input split p = list(map(lambda x: (1+x)/2, p)) p list(map(lambda x: (1+x)/2, p)) list map(lambda x: (1+x)/2, p) map lambda x: (1+x)/2 (1+x)/2 1+x 1 x 2 x p s = [0] s [0] 0 num = 0 num 0 for i in range(n):
  num += p[i]
  s.append(num) i range(n) range n num += p[i] num p[i] p i s.append(num) s.append s append num l = [] l [] for i in range(n - k + 1):
  l.append(s[i+k]-s[i]) i range(n - k + 1) range n - k + 1 n - k n k 1 l.append(s[i+k]-s[i]) l.append l append s[i+k]-s[i] s[i+k] s i+k i k s[i] s i print(max(l)) print max(l) max l k = map(int, input().split()) map(int, input().split()) k s = [0] [0] s p = list(map(lambda x: (1+x)/2, p)) list(map(lambda x: (1+x)/2, p)) p num += p[i] p[i] num l = [] [] l p = list(map(int, input().split())) list(map(int, input().split())) p n, k = map(int, input().split()) map(int, input().split()) n num = 0 0 num
n, k = map(int, input().split())
p = list(map(int, input().split()))

p = list(map(lambda x: (1+x)/2, p))
s = [0]
num = 0
for i in range(n):
  num += p[i]
  s.append(num)
l = []
for i in range(n - k + 1):
  l.append(s[i+k]-s[i])

print(max(l))
