n,k = map(int,input().split())
li = list(map(int,input().split()))
licsum = [0]
for i in range(n):
    licsum.append(licsum[i] + li[i])
lia = []
for i in range(n-k+1):
    a = licsum[k+i] - licsum[i] + k
    lia.append(float(a)/2)
print(max(lia)) n,k = map(int,input().split()) n map(int,input().split()) map int input().split() ().split () input split k li = list(map(int,input().split())) li list(map(int,input().split())) list map(int,input().split()) map int input().split() ().split () input split licsum = [0] licsum [0] 0 for i in range(n):
    licsum.append(licsum[i] + li[i]) i range(n) range n licsum.append(licsum[i] + li[i]) licsum.append licsum append licsum[i] + li[i] licsum[i] licsum i li[i] li i lia = [] lia [] for i in range(n-k+1):
    a = licsum[k+i] - licsum[i] + k
    lia.append(float(a)/2) i range(n-k+1) range n-k+1 n-k n k 1 a = licsum[k+i] - licsum[i] + k a licsum[k+i] - licsum[i] + k licsum[k+i] - licsum[i] licsum[k+i] licsum k+i k i licsum[i] licsum i k lia.append(float(a)/2) lia.append lia append float(a)/2 float(a) float a 2 print(max(lia)) print max(lia) max lia li = list(map(int,input().split())) list(map(int,input().split())) li k = map(int,input().split()) map(int,input().split()) k a = licsum[k+i] - licsum[i] + k licsum[k+i] - licsum[i] + k a licsum = [0] [0] licsum n,k = map(int,input().split()) map(int,input().split()) n lia = [] [] lia
n,k = map(int,input().split())
li = list(map(int,input().split()))
licsum = [0]
for i in range(n):
    licsum.append(licsum[i] + li[i])
lia = []
for i in range(n-k+1):
    a = licsum[k+i] - licsum[i] + k
    lia.append(float(a)/2)
print(max(lia))